That is one possible scenario. Another possible scenario:"You suck (so much that we won't honor our commitment to you and will do our best to make things awful for you so that you want to leave)" is the problem.
I assume this will have zero impact on northwestern basketball or Chris Collins' career.
Player: Coach, you need to give me more playing time.
Coach: You suck too much to get more playing time.
Player: Then I want to transfer someplace where I can get more playing time.
Coach: That might be a good idea.
I'm not saying that is what happened here, as I have no inside knowledge. Just noting that it is another plausible scenario. Let's see what NU's side of the story is.