Grantham must be difficult to work with, he's a good DC but doesn't stay anywhere long. He and Petrino probably got along about as well as a wolf and a rabbit.
No way UL wanted Todd to leave. At least from what I heard, there's more behind the scenes with how people got along with each other. Petrino is a mess of a HC. Good coach, but terrible person.
Why on Earth anyone would hire Peter Sirmon as the defensive coordinator is beyond me, Grantham is a solid DC but couldn't hold many opponents very well what do they think Sirmon will be able to do? Louisville will have to score 100 points a game next year.