Tyson is one of the most interesting sports figures of the last century IMO. Dude is very intelligent; I would highly recommend watching his documentary.
He couldn't cope with D'Amato's death and went off the deep end. D'Amato was the only person that he trusted/Tyson would listen to.
Tyson is fascinating. Cus D'amato knew he needed a team in place to keep him from unraveling, and knew that his time was limited, and so he put a team in place for Tyson. Rooney as trainer. Cayton/Jacobs as managers/agents. And a couple other guys as friends/confidants.
Tyson needed that infrastructure, and it all unraveled when Robin Givens and Don King got in his ear. Actually it all unraveled after Jacobs died. Jacobs was the manager that Tyson trusted as a friend. Cayton didn't have that kind of relationship with Tyson and had no way of keeping King out of the mix.
After Spinks, he fired Cayton and Rooney, and that was that. The style that Tyson learned through Cus via Rooney was highly technical and required constant reinforcement (read: proper training). He never got that after he fired Rooney.