I looked at some archived articles from the paper covering Marshalltown where he played junior college ball. First off, I think it's fairly clear that Coleman decided to go the prep school and juco route because of grades as teams like Nebraska, and Marquette were recruiting him heavily in high school. This would also explain his connection with Tony Benford who was the primary recruiter for Marquette around the time Coleman was in high school. So Benford knows this kid and what he is capable of.
So why did he leave Nebraska? Tim Miles had taken over for the fired Doc Sadler and was going in another direction as evidenced by this quote:
That being said it also appears that Miles still had interest in Coleman as stated here:
There is a similarity with Coleman's situation and John Odoh as Odoh had developed a strong relationship with Johnny Jones and Shawn Forrest:
Here's the entire article: http://meangreenblog...-up-push-f.html
Coleman and Nebraska to go separate ways (Update)