I believe he thought he was going to come into Buffalo and everything was going to come easy for him and he would be one of the players to turn the Bills around. When it didn't happen overnight, he got frustrated and either stopped caring, or wanted out as soon as he could.
It's too bad, I still think he has great talent - if only he'd put in the work.
I remember being really excited when we traded up for him. Boy, was I wrong....