Self-promotion was not a motive in light of the fact that the Pharisees were persecuting the new movement. Peter was humbled. Both Acts and Mark demonstrate this in the accounts. Peter was preaching that Jesus was the son of God and had been resurrected from the dead. That's not a very good way to prop oneself up in the face of fierce, dogmatic Judaic opposition, especially when Rome was holding the puppet strings of the High Priest.That depends: was the author delusional? Did the author suffer from egomania, in that he wanted to prop himself up in some way?
Picture yourself in Peter's sandals.
"Yes you killed our leader for treason but guess what? He's still alive! Epic failure Pharisees! Neener neener!"
By preaching that message, Peter and the apostles were setting themselves up for intense opposition.
Well that's true of modern writing, but that style of detail wasn't used in ancient fictitious writing. So that argument really doesn't go far.Each of those examples, the author would have been intending to communicated "history", but all the while, he was writing fiction.
Human biases again...