Hiring Zo gives them some cover. He aint firing either one of them either. Not hiring Zo means they're the ones solely responsible. That aint self preservation. They're on a island.
He's the HC. Until he gets fired he's the most powerful person in the program. Those guys have never handed over the type of power that Zo would deserve.
The surprise was that this was even a consideration. Manny would've been the only coach in America to willingly give over a piece of their program to an outside name.