We'll probably never know (at least publicly), but I wonder what the coaching staff thought they were getting with him vs. what he turned out to be.
It may well be that he's been just fine in the eyes of the staff, but that the competition on the roster has just been really competitive, especially on this year's team. His best chance to play might have been 2 years ago, he did get some minutes in Big East play here and there as the 8th man, but while that team only played 7 guys, it was well-stocked in three point shooting and at the positions Mookie can play. I commend him for handling a humbling 4 years pretty well though.