He was in over his head.
Tactically, is 'offensive' sets were over the heads of the kids he was playing. Worse yet, he'd keep on doing it even when it wasn't working. I can count on two hands the times I saw them run half court offense and the team was actively not pushing the ball. Defensively, they were pretty good, so I can't fault him there.
His recruiting was lazy. And at times neglected.
Yes, transfers happen everywhere, but not to core guy you just got done fighting recruiting battles in order to get. Maybe Jackson's dad was a , but how do you not figure this out during recruiting? Did he not see how green Enoch was when he recruited him? Every year from 2015-on was more and more duct tape - and even crazier than that - he didn't have as many scholarships to have to use. There's literally no excuse.
Rumors of the issues on the staff, staff turnover, poor strength and conditioning - he was pretty bad there.
He alienated a lot of alumni and especially Jim Calhoun.
And administratively he was just sloppy. The NCAA violations were sloppy, lazy violations. But again - that's how everything else in the program was treated. He was coasting or trying to. Or was just clueless as to the approach he should take.
I've met Ollie before and my take for a while now is he's just an NBA guy who's not built for the college level. He's the kind of grizzled vet that puts his arm around the rookies and teaches them where to go an eat on the road, helps them buy their first suit, etc. He's Drunk Uncle Kevin - and in the pros - that's a good thing. In college, you need more of a father figure - there was alot of talk of Ollie being too buddy buddy with certain guys and less so with others.. it all kind of sings to that.
Coaching in the NBA is pretty seamless in that you prepare for games, coach guys, meet with your GM and you can be selective every year about what you're bringing in and out of your organization. College is different, there's a lot more administrative BS, there's alums to deal with and kids with a fraction of the talent who take a lot more hands-on care. It's a more comprehensive job.
Then you watch guys this year with this coach, and go elsewhere and work with other coaches and, well... I mean how people just don't see the trend or the common denominator here is absolutely, completely beyond me.
I think it started off as just not being prepared for that kind of responsibility and as things wore on, it got worse and worse - and more obvious that he wasn't ready for that kind of a program. That's why he doesn't have a job. But he was bad at almost every single aspect of being a college head coach at a program this size.