There are probably a plethora of things. One might be his lacking in knowing what he needs talent wise to run his offense. The idea was, you have your OL engage their man for a second and then let them through. This gets them in your backfield while your quick witted, accurate qb whips it out to a speedster in space with a minimum of defenders. When the defense tries to adjust you run quick draws to keep them off balance. This teeter totters throughout the game. It's actually not a bad offense if you have that qb and good skill players.
So, he unexplainably focuses on recruiting qb's the direct opposite of what he needed and then tried to force square pegs in that round hole.
AM, then the skinny fast legacy kid who wasn't anywhere near what he needed, even less so than AM. In fact his only other serious recruit wasn't even a real qb at all. The only other qb's brought here were long term projects that should probably transfer to a lesser division, even then I don't know if they'll find success anywhere.
AM is a one trick pony who plays for a coach who understands his horse. He is limited to quick, low risk throws and purposeful runs. Frost never understood what he had. His offense just degraded into a lot of qb draws and poor reads.