The new GM didn't want him. Jackson didn't want to be there (lobbied for Clippers and Nets job this past offseason.) He clearly needs to pick his own assistants, having clashed with two top assistants and Scalabrine (but I think Scal was probably to blame for a lot of his undoing.)

At the same time, a lot of those things could be said about many coaches in the NBA.

Personally, from the stories I've heard, I think he's an asshole but he clearly a great motivator and solid coach and I think he could have continued success and less controversy if he went somewhere else. Detroit might be the best landing spot for him.