Reading some of the stories that have come out since the Carthon firing it seems amazing this guy was able to keep the job as long as he did.
There have been a few reports about him calling the wrong protections with the plays he called more than a few times. His negative aggressive personality and the way he treated players didn't go very well either.
It's a little troubling to me that Crennel stood by this incompetent idiot for so long. It should have been obvious from early on that he couldn't handle the job.