For starters, Martin is a logical player to move. He’s a 32 year-old with a long history of scoring efficiently and he has a contract that is now considered favorable. Martin also plays the same primary position as second-year players Andrew Wiggins and Zach LaVine.
Relieving the logjam could be achieved by moving a very movable piece, so it only makes sense. The timing is interesting as the team started the season well and isn’t especially deep with NBA-caliber rotation players, but seems coincide with a minor wrist issue that cause Martin to miss a game a couple of weeks ago.