Because he was cut from the team?
If "cut" is too strong of word, he was kindly asked to look at other opportunities. He didn't magically wake up this morning after an entire off season and think, "I want to go to a new school..."
Why would the coaching staff "cut" a player that could add depth and potentially contribute, at least in practice on the scout team? Your suggestion makes no sense. I'm sure that there are tough conversations about the future for certain kids, but this would be done after the season is over. As others have mentioned, it's possible that he didn't like being so far down on the depth chart and couldn't see himself surpassing anyone above him