There are politicians, coaches, CEOs, etc. that knowingly take bad decisions. They just do. That doesn't make them intelectually speaking dumb and it also doesn't mean they don't know how to teach players how to play the college game in the case of a coach.
Faust, Ty, Davie and Weis fundamentally did not know -- or weren't willing in the case of Ty -- how to coach college kids and run an overall program. They could not take a high school player and figure out what position to play them at to maximize their talent and how to teach them how to play the college game. They also were incapable of seeing what was happening, understanding it, and then coming up with a way to teach the kids how to execute.
I actually think Kelly does know what's happening, does know what will fix it, does know how to coach the kids to do what has to happen -- but he flat out refuses to do it. For reasons I will never understand Kelly would rather lose games running his system than win games running a different system. There is something broken in his brain where he measures his success based on proving his system can win a title.
Weis also was/is a very smart man. Weis also could see what was wrong -- and I think offensively could see it real-time during games. Weis was incapable of teaching college kids how to do what he wanted them to do, so he could not implement what he had in his mind. It is why he is very good in the NFL where someone else teaches the players how to do what's in his mind.