My thoughts, for what they are worth...
I seem to remember hearing on this board from current SU students that Chris wasn't really taking the academic part of being at SU seriously, because he was planning on being a one and done player. Could this be playing a role in his decision? Additionally, I would have to think he missed some class time due to his injury, surgery and rehab, possibly putting him even further behind academically.
My other thought has to do with his timetable to return. I read in several articles that he was hoping to be ready to return in January. If our schedule next year is similar to this year he would be missing the entire non-conference season. If he was able to return when expected, which doesn't always happen with these types of injuries, he would be thrown right into the ACC schedule against tougher opponents. My point being, even if Chris came back next year, it seems that many fans were being unrealistic in their expectations. I was looking at a best case scenario of Chris making it back for ACC play, working up to 20-25 minutes of action by the end of the season with his points and rebounds per game close to what they were this year. Nothing wrong with those numbers, but certainly not a death sentence for the 15-16 squad if he didn't return.
As an alum and proud supporter of everything SU, I wish him the best. I am hopeful a team will take a chance on him and draft him in the first round so he can have a guaranteed contract. Off the top of my head the only comparable I can think of is Nerlens Noel. Of course Noel had almost an entire, and more productive, season at Kentucky under his belt when he injured his knee. I truly hope I am wrong, but I don't see an NBA team using a first round pick on a player who played sixteen college games, was only dominant in three or four against inferior competition, and is coming off major knee surgery.