I'm not convinced that it was entirely just Fulmer interfering directly. There seemed to have been a ton of pushback from the players about how hard the new system was, and how complicated the terminology was, and how they basically resented having to do anything different than they'd already been doing. It seems pretty clear that even if Clawson had had a completely free hand, a lot of the players would still have refused to buy into his system and put the work in.
Which goes to the culture of the program, of course. Which is on the head coach.