just opinions..
On Bo, he wanted out. The 'fish bowl' was killing him and to me, the lashing out and temper outbursts were symptoms of this, if not downright self sabotage.
Eichorst was calling the shots, not Riley.. Riley was just a yes man and nice guy, which is how he still kept getting hired post Nebraska.
Frost was in over his head and too stubborn.. He probably would have done better at any other school.
Rhule, one thing I have noticed so far, is how he pandered to the fan base a little bit.. changing QB's (some say to injury) but he went along with the fan base when they wanted a change.
I criticized his eval on Sims and making the QB and RB rooms worse before the season started, but I also think HH was available for the Cockeye game and should have played him in an attempt to get the 6th win. Purdy, is winless, and I don't think any coach would gamble on that if they were trying to get that 6th win. So to me, he chose appeasing the fan base more than wanting to get bowl eligible.
I an interested to see what happens on the offensive side of the ball in the offseason. I have a fear that it gets worse.. but let's hope not.