In answering this question I reference some areas that may seem off-topic for the question but included to both build the answer and avoid more hanging questions. I feel the elaboration is warranted since the topic is a standing important point of confusion
The example of Abraham
I think the best way to understand this is when Abraham (Ibrahim, Avram) the great ancestor of both Isa (Yeshua, Jesus) pbuh and Muhammed (pbuh) was in the process of sacrificing his son (Ismail (Ishmael) according to Islamic tradition, Isaac according to Old Testament).
The custom back then with Abraham’s folk was to sacrifice their eldest son to their idol gods in times of drought and famine. Abraham rejected these idol gods and preached his folk to forsake their false gods and worship Allah and Allah only. His audience for the most part rejected his message and taunted him to sacrifice his own son to Allah if he believed in Allah so much. He had a dream where he was requested to sacrifice his son (Quran 37:102)
Human sacrifice, especially ones own children may seem the ultimate in evil and cruelty, but now in the 21st century it persists for not only our eldest sons but all sons and daughters are sacrificed to military campaigns to the altar of false gods and flags with the full encouragement of their parents. The physical methods are different but ideologically the same.
The narrative in both the Quran and Old Testament say that this was the ultimate test of faith for Abraham (Quran 37:106).
Abraham demonstrated that he was willing to sacrifice everything including his son for the sake of Allah, and his son also did not waver in letting his father take his life if that was the will of Allah (Quran 37:102).
Allah of course did not allow the actual sacrifice and commanded Abraham to sacrifice a sheep instead (Quran 37:107). After passing this ultimate test of faith, Allah rewarded Abraham by promising prophets and the scriptures to his descendants, and blessing the world through his seed.
Indeed, tradition follows that Muhammed was a descendant of Ismail (Ishmael) and all the prophets of Bani Israel (Moses, David, Solomon, John the Baptist, Jesus, etc) were descendants of Isaac (Quran 6:84). Israel is another name for Jacob (Yakub), who was son of Isaac. Israel's 12 sons and their descendants, the 12 tribes of Israel, are collectively referred to in the Quran as children of Israel (Bani Israel).
Mission of Jesus, rejection of his message and mission
Jesus (Isa, Yeshua) was sent to Bani Israel as their messiah and savior. Part of his mission was to relieve them of some of their burdens (Quran 3:50) (relax some dietary restrictions, sabbath) and to demonstrate that mercy was much closer to piety than laws and punishments. He also strove to restore all faith and worship to Allah as the bani Israel were already corrupting themselves by worshiping and cherishing partners to Allah (money, material goods, children, ancestors, tribe worship, etc).
Jesus like Yahya (John the baptist), and numerous prophets before who were slain, would not waiver in risking their lives in the service of Allah. That being said I think that the example of Abraham and his son gives us important insight about the nature of Allah and the supposed blood sacrifice crucifixion of Jesus.
Allah did not allow sacrifice of Jesus, as with Abraham's son
Just as Allah did not allow the sacrifice of Abraham's son, or any human sacrifice, clearly forbidden in (Quran 5:32, 17:33), similarly Allah would not have allowed the death of his messenger Isa ibn Merriem (Jesus, son of Mary) as a sacrifice.
Allah needs nothing, source of all mercy and beneficience
Allah has no need for human blood, Christ’s or anyone's. Allah ‘needs’ nothing period. We need Allah. To believe otherwise, is very sinful. The Christian belief is that God the Father ‘needed the blood of his only begotten son to forgive the sins of everyone. All you have to do is just believe that Christ offered himself as a blood sacrifice to the heavenly Father and you are ‘saved’.
The enormity of this misconception goes way beyond being ludicrous. It portrays Allah as a horrific bloodthirsty entity, and obviously insulting and blasphemous to Muslims. It is impossible for Christians to glorify Christ and his supposed crucifixion without darkening the heavenly Father.
Was there a deception? Are we entitled to truth and light if we reject it?
Thus just as Allah did not need and did not allow the sacrifice of Abraham's son, as the aya states Allah did not allow the crucifixion of Isa ibn Merriem. However, the aya
(4:157) adds that the crucifixion appeared real to the witnesses of the event.
The OP was confused as to why Allah would make it appear as an actual crucifixion as though there was a deception. This question pre-supposes an arrogant expectation that Allah owes his creation the complete perception of all reality. This expectation is way out of place. Allah owes us nothing. Everything, our lives, our sustenance, the world, the universe, our family, etc are gifts from Allah. Allah is above all and is not obliged to provide anything. Our attitude should always be gratitude. Appreciation, not expectation. Shukur, not Kufur.
All our faculties sight, hearing, scents, etc are included in all the providences of Allah. Everything we see or hear is through Allah’s permission ‘iznee’ (Quran 2:255, 6:103, 35:22). We perceive what Allah permits us to perceive. What our eyes do see is a tiny fraction of reality.
This is particularly relevant to the folk who came to witness the crucifixion. Allah sends his messenger as a mercy providing truth and light to this folk who reject him and condemned him to death after all the healing, guidance, and wisdom he provided and the miracles he performed. Even his disciples fled and those that were cornered and questioned as was Simon Peter denied having known him.
Isa was rejected, spat upon, tortured, humiliated, and condemned like a criminal. To expect Allah to provide truth and reality to those who have so violently and murderously rejected truth is very arrogant. See Quran 14:4.
If I provided you a gift out of the goodness of my heart expecting nothing in return, but you return the favor by rejecting the gift and trying to kill me, do you expect me to keep providing you gifts?
Nay, Jesus’s audience rejected the truth, love, guidance, and mercy provided by Allah through his messenger. Despite of this, despite of us, Allah sent his final messenger, Muhammed as a mercy, and blessing for all the nations (Quran 21:107). There is nothing binding Allah to do this. Allah is the most compassionate, most merciful.
Cruci 'Fiction'
So let our Christian brothers heal their hearts and minds that Jesus did not die on the cross. Allah is all beneficent. The most beneficent does not need human sacrifice to forgive sins. The alleged crucifixion is a cruci’fiction’.
If our Christian brethren want to know and live the true message of Jesus, all they have to do is embrace Islam and follow the teachings and example of the prophet Muhammed (pbuh).
This does not imply in any way that Muhammed is superior to Jesus. All the messengers of Allah had the same mission and it says in the Quran that we must not distinguish between them (2:285).
So where did this blood sacrifice notion come from?
How else can Paul and the other apostles come to terms with the crucifixion of the messiah. The old testament describes the messiah as the warrior king who will come and deliver the tribe Israel from her enemies and establish Allah’s kingdom on earth. Instead they saw their master brutalized and murdered. If he didn't perform all the miracles and confirmed that his teachings were authentic of divine origin, they would have dismissed him as a false prophet.
Even though the interpretation to explain this event is ludicrous and blasphemous as stated earlier, there is not any way to explain the reason for the crucifixion of the messiah who was sent by a benevolent God. On the contrary this is malevolence. It is very difficult to explain malevolent results from a benevolent God.
The Old Testament is often referenced to try explain the meaning and reason for the crucifixion of Jesus. There are numerous references in the Pentateuch, particularly numerous in Leviticus, where Jehova commands the Israelites to offer animal sacrifices, particularly during holidays like Passover. In the gospels also Joseph, husband of Mary and stepfather to Jesus, is mentioned sacrificing a pigeon at the temple after the birth of Jesus. The gospels mention Jesus getting upset with money extraction for passover sacrifices at the temple. He did not object to the animal sacrifices themselves.
Quran clarifies purpose of animal sacrifice
The Quran clarifies in surah 22 aya 36-37 that that blood and meat from the animal sacrifice does not reach Allah, but the piety from us earns us sevap (good deeds) in distributing the meat, skin, and other products to the needy. Indeed in many cases from our prophet's time until the present day, the sacrifice festival once a year is the only time the very needy have access to meat protein. This clarifies the purpose of animal sacrifices. Allah obviously does not need them, but rather a method of worship where the believers with means give up some of their worldly possessions to feed and clothe the needy and in so doing bind the community closer together and closer to Allah. It is another form of zekat (alms giving).
The clarification in the Quran regarding animal sacrifices is in stark contrast to the verses in Leviticus of the Old Testament where Jehova commands the Israelites to make burnt offerings of animal sacrifices because the smell of the burnt offerings is “pleasing to the lord”. This implies that Jehova derives pleasure sensations from burnt flesh of his animal creation and also this cruel pleasure is more important than feeding and clothing the destitute. This is not an all benevolent God, and we can see the roots of where the sacrifice of Christ notion originates.
Modern Interpretations of Sacrifices
We can put aside the literal meaning of burnt offerings for a metaphorical one where we give up something that we cherish in this world (not humans) with no expectation of any kind of return, material or spiritual, to demonstrate that we cherish, and worship Allah only, and ascribe no partners to him.
In our prophet’s and Abraham’s time, people cherished their herds of sheep, goats, camels, and cattle. In our time we cherish all kinds of things, notions, flags, ideologies, relationships, etc. There is a thin line between cherishing the above and worshiping them as substitutes or partners to Allah. They can become false gods. If we cherish our work and our careers, we must remember to sacrifice the time needed for salaat when the times come. Otherwise, the work, money earned, or career is considered a partner to Allah or more important to Allah. If anything in this life ends up being more important to us than Allah, give it up as a the ancient Israelites gave up the animals which were very important to them.
