He left on his own. He could have stayed.
Freeman et al, didn't decide the starting qb out of spring camp. By most accounts, Angeli was told he was, at best, #2 on the depth chart, neither as good a runner as Minchey nor as good a passer as Carr. Coaches make decisions all the time re: playing time. It is tough when you play the one position (except maybe the kicker/punter and long snapper) where only one guy gets to play. So he read the room, saw his competition face-to-face, heard what the coaches had to say and he made a decision to leave.
Yes, Angeli has put up good numbers against the likes of UConn and Colgate. But let's face it: Colgate/UConn ain't exactly Miami or A&M. Note: And we didn't lose either of our games because of qb play. And Syracuse won't play as good a team as either of them until they play Miami in November. As I remember there were folks saying similar things about Buchner and Jurkovec as they are about Angeli.
Time will tell if Angeli turns out to be a NFL draft pick or just another guy who did a good job at what he loves to do. I wish him luck.