I think he hit his ceiling.
- isn't getting any taller
- is already a good defender
- is already strong enough
- is a good (not great) ball-handler, good enough
- he isn't ever going to be a vertical player (above the rim)
- shooting is his main obstacle, and I don't think he will ever become a good shooter, but he does need to become a consistent adequate shooter. Perhaps not having to go to classes & study will give him more time to work on his shot. He wasn't going to come back and suddenly become a Good shooter.
- Also, right or wrong, the NBA views players who are JRs or SRs as having something wrong with them. Actually I think they fall in love with the ceiling of the younger players, and think the upperclassmen have approached their ceiling. And while I agree that usually the younger players that you've seen less might have a higher ceiling, they also have a lower floor.