Scott Frost is a prick. It's just who he is.
If you were at school in Lincoln during his time, he was not a popular guy amongst most of the team or anyone else in Lincoln. He was tolerated by fans and teammates because he's a good QB but he's not the guy you pal around or have a beer with. He had a small circle of friends, most of them his buddies from Wood River and jock chasers like Matt Davison.
You can get away with being a prick when you're winning but not when you're the worst coach in school history.