Why did Adam say that he being sent to the world was predestined and not something for which he should be answerable?

Question

I came across the below encounter of Musa and Adam. Why did Adam say it was predestined? In Islam we are taught that everything is written in the book of destiny but the choices are still in our hand.

Abu Hurairah narrated that Allah's Messenger said: "Adam and Moses argued with each other. Moses said to Adam: Your sin expelled you from Paradise. Adam said to him: 'You are Moses whom Allah selected as His messenger and as the one to whom He spoke directly. Yet you blame me for a thing which had already been written in my fate before my Creation?' Allah's Prophet Muhammad said twice: "So, Adam outclassed Moses." (Sahih al-Bukhari)

Umar Ibn Al-Khattab also narrated that Prophet Muhammad said: "Moses said: 'My Lord! May I see Adam who removed us and himself from the Paradise?' So Allah made him see Adam, and he said to him: 'Are you Adam?' Adam said: 'Yes.' And he said: 'Were you the one in whom Allah breathed His spirit, and before whom He bowed His angels, and to whom He taught the names of all things?' Adam answered: 'Yes.' So Moses said: 'What made you remove us and yourself from Paradise?' Adam said unto him: 'Who are you?' He said: 'I am Moses.' Adam said: 'So you are Moses the prophet of the Children of Israel. Were you the one Allah spoke to directly?' Moses answered: 'Yes.' Adam said: 'Why do you blame me for a matter which Allah had predestined?"' So Allah's Prophet Muhammad said twice. "Adam outclassed Moses." (Sunan abi Dawod)

Answer 1

Cause Adam Alayhi salaam is not truly answerable for that. He 'forgot' and made an error in his judgement, he did not willfully disobey Allah Subhanahu wa ta'ala.

And We had already taken a promise from Adam before, but he forgot; and We found not in him determination.

(Surah Ta-Ha 115)

His going down to the earth was already decided beforehand. This is the conversation between Allah Subhanahu wa ta'ala and the Malaa'ikah:

And [mention, O Muhammad], when your Lord said to the angels, "Indeed, I will make upon the earth a successive authority." They said, "Will You place upon it one who causes corruption therein and sheds blood, while we declare Your praise and sanctify You?" Allah said, "Indeed, I know that which you do not know."

(Surah Al-Baqarah 30)