To open your question you're asking why do prophets need assurances with faith or success against their enemies? Why don't they just blast their way through with everything.
tl;dr: Prophets are humans. Super Great humans. But there is no limit in learning more, having more faith. Additionally they're defeat-able.
Discussion about Prophet Ibrahim (PBUH)
لِلرُّؤْیَهًِْ فَضْلٌ عَلَی الْخَبَرِ.
Seeing is superior to news (you hear)
ٱلَّذِينَ يُؤْمِنُونَ بِٱلْغَيْبِ وَيُقِيمُونَ ٱلصَّلَوٰةَ وَمِمَّا رَزَقْنَـٰهُمْ يُنفِقُونَ
who believe in the unseen,1 establish prayer, and donate from what We
have provided for them,
Believers have faith above others, because they believe in something they haven't seen with their own eyes. But there different levels of this belief. Prophets have a higher level of belief than me and you. Then among prophets themselves some of them are better than the other We have chosen some of those messengers above others Baqara:253
That being said prophet Ibrahim is never to be said a non-believer. All he's asking is more proof. There is never an end to how much you believe in Allah. Even though Prophet Muhammad is the most humblest of all prophets and has the most knowledge his knowledge could always be more and more and more.
Prophet Ibrahim isn't saying to Allah: "Oh Allah...I don't think you can bring anything back to life." He's saying "لیطمئن قلبی"
وَإِذْ قَالَ إِبْرَٰهِـۧمُ رَبِّ أَرِنِى كَيْفَ تُحْىِ ٱلْمَوْتَىٰ ۖ قَالَ أَوَلَمْ تُؤْمِن ۖ قَالَ بَلَىٰ وَلَـٰكِن لِّيَطْمَئِنَّ قَلْبِى
ۖ قَالَ فَخُذْ أَرْبَعَةًۭ مِّنَ ٱلطَّيْرِ فَصُرْهُنَّ إِلَيْكَ ثُمَّ
ٱجْعَلْ عَلَىٰ كُلِّ جَبَلٍۢ مِّنْهُنَّ جُزْءًۭا ثُمَّ ٱدْعُهُنَّ
يَأْتِينَكَ سَعْيًۭا ۚ وَٱعْلَمْ أَنَّ ٱللَّهَ عَزِيزٌ حَكِيمٌۭ
And ˹remember˺ when Abraham said, “My Lord! Show me how you give life
to the dead.” Allah responded, “Do you not believe?” Abraham replied,
“Yes I do, but just so my heart can be reassured.”
just for my own extra assurance. He's not saying I'm disbeliever, but there's always value in seeing something vs. just believing in it. I mean think about it, if you were given the opportunity see the dead being brought back to life, wouldn't you be curious too?! I know I would.
FWIW Allah is always giving Muslims assurances for heaven and hell, describing it through different ways. He could have just said it's a nice cozy place, but he does't do that. He goes into details about its rivers, houris, fruits, weather, its good feeling. And same with hell, how burning it is. Why? Because we get a better sense. Prophet Ibrahim wanted that better sense.
FWIW 4 other verses in Quran talk about heart assurance. See this search
Discussion about Prophet Ibrahim (PBUH)
Prophet Moses is again a human. He can be afraid. As was prophet Mohammad, when he needed assurancesMa'eda:67 when he felt threatened from people.
Prophet's haven't always succeeded. Abel was killed by his brother Cain. Noah only had enough followers to fill in a single ship. They were in many battles. And they never knew if that battle of theirs was the battle that they die in or not.
اَيْنَ الطَّالِبُ بِذُحُوْلِ الْاَنْبِيَآءِ وَ اَبْنَآءِ الْاَنْبِيَآءِ؟
Where is the defender of the traditions of the Prophets and their
Prophets were killed. Prophet Yahya was beheaded. Prophet Zacceria was cut while he was in a tree. If once a prophet knew he was a prophet and then he was to succeed at every end, then it wouldn't really be a test for the people because the prophet was the one who always won. So no! Prophets were betrayed and bested by others. Allah doesn't promise that he would send his angles or the wind and earth for every battle. He can do that. But may choose not to. He let's them fail, so hypocrites can be revealed when they switch sides. Remember hypocrites are always want to be on the winning side. If a prophet always wins, then there's no way for their hypocrisy to be revealed.
Prophet Moses after all his success against the Pharoah, the people turned against his second in command, Prophet Aaron, his brother and worshipped a calf. Prophet Moses was betrayed by Samiri
فَأَخْرَجَ لَهُمْ عِجْلًۭا جَسَدًۭا لَّهُۥ خُوَارٌۭ فَقَالُوا۟ هَـٰذَآ إِلَـٰهُكُمْ وَإِلَـٰهُ مُوسَىٰ فَنَسِىَ
Then he brought out
for them a corporeal calf that had a lowing (voice); so they said,
"This is your god, and the god of Musa, (Moses) yet he has forgotten."