Nobody seems willing to give a definitive answer as to why he has to leave. There have been rumors of weed, fighting with teammates, and being a,poor teammate, but nothing concrete.
The only thing you mentioned that's incorrect is the fighting; the rumored Roach/Tevin locker room brawl didn't happen. People pointed to a shiner, but if you go back and look at the days leading up to that game, Roach already had swelling around his eye (a source told me it was a reaction to medication). Those two were buddies; there's a reason they got suspended together and for the same number of games at the start of that season, it's because they got caught for the same thing. (Some day when it's legalized, this will stop being an issue in college basketball.) These things all contributed to him getting tossed, but the final straw I'm not going to get into in any detail on a public board except to say Tevin doesn't really deal with authority figures well. If you've seen me reference elsewhere how much I'm going to enjoy watching him interact with a coach that turns the screws like Avery, that's why. Maybe Tevin has settled down since he was in Austin, I hope for his sake he has.