It all begins and ends with culture. Aggy culture emphasizes appearances above all else. That's not a foundation upon which anything resembling success can be built. I don't care if you're Nick Saban with an annual $200M to spend on players, when your school's culture is as deficient in self awareness, common sense, and substance as Texas A&M's is, the inevitable result is an undisciplined, underachieving, unmotivated group of mercenaries who fold after being punched in the mouth and will transfer after one season if they aren't coddled and don't get the playing time they feel they should be getting. You might think a hard-nosed disciplinarian like Saban could overcome these tendencies and build a winning subculture, but that would never happen because Aggy can't get out of their own way--as in, they're pathologically incapable of resisting the urge to meddle with the way their team is coached if the team is not wasting a sufficient amount of time and energy on Aggy traditions and values, e.g., all of those things that are completely antithetical to having a winning subculture.
To put it succinctly, you cannot be Aggy and successful at the same time.