Why not make the $ AND develop with better competition while he's still healthy. He and his wife both speak Italian from what I hear so they could make it work just fine I'm sure even if Europe were long-term.
I don't know enough to say if getting an NBA contract from college is more likely or from European leagues but there are enough European players in the NBA to make me think they have a pretty strong scouting presence there. Plus he gets new coaching. This is his career. Makes sense to me.