The difference between Tom Osborne Nice and Mike Riley Nice. Osborne was a Nice Guy, but he could still be a total hardass as a coach, and would never accept a lack of effort from his scout team players, let alone his starters. Mike Riley... not so much. He never took control of his team, and as much as some wanted to blame Bo for that, let's be real: he never would have. And this will probably rustle some Jimmies, but there's another coach that I really think would have had the same problem: Turner Gill. Yes, KU is a less than ideal place to coach football, but as much as anything his problem there was that he never took control of his players.
Some guys have the personality for it, some don't.