1- all of those leaving early are married, so might have some to do with knowing the NBA was a longshot and wanting to get to it in europe of somewhere earning.
2- Mika seemed pretty open about the chemistry on the team etc. He might be telling guys like Elijah and Yoeli how great it has been for him etc.
3- if you are pretty certain that the NBA isn't in your future and you don't feel like you are receiving sufficient player development then, leaving early could be a smart move, you can always finish the last year of your degree later on.
4- none of this could be true and it could just be a rash of bad luck (probably not though)