I think Bob actually wanted to fire Norvell. I've heard from a few people on the periphery on the program Norvell's gotten lazy, especially in the off season. Plus Bob was pissed that almost none their receivers have gotten better with Jay coaching them.
Also, Jerry Montgomery has come in and kicked ass. Some think Bob's realized some have gotten complacent. Montgomery's put other coaches to shame with his work ethic and recruiting. Bob wants more like him like they had 15 years ago.
