Trump is not going to prison. He has a bolt hole; worst case for him is living a very comfortable exile in Saudi Arabia. He can or has stashed some money offshore, the Saudis have a history of harboring disgraced leaders and the prince likes making Biden, the Democrats, and westerners in general look weak. Trump being rapey, power mad, and corrupt also makes him someone the prince can relate to.
It won't even come to that. He'll use the corrupt US legal system against itself and never go anywhere near a prison. I'm not even convinced he'll be charged with anything, except maybe some financial stuff, and that'll be fines and little more. The US is stacked against everyday people and rigged for the rich. Even in a worse case scenario, like home confinement or a prison sentence, the next Republican President ( not far off) will pardon him.
See if I'm wrong. I've been making predictions about this guy for years and never been wrong, taking the aerial view.
I can't imagine the MBS putting up with Trump any more than he has to.
(Is he going to show Trump how to behead people?)