Yeah, its all either motivated to see if they can get some $ or get some playing time.
...or a mix of both.
Kimani Hamilton basically didnt play for us last season and averaged 15ppg, 7.2rpg, and 2.3apg this season. Based on where he landed, he was successful from a playing time perspective.
Murphy likely looked around a bit, saw what he could likely have at MSU vs elsewhere, and decided MSU was his best option at the time. The fact that he is back at MSU shows MSU also looked and decided he was the best option at the time.