The decision doesn't come as a huge surprise. Jon Krawczynski of The Athletic reported May 3 that Crawford would opt out, noting that Crawford was unhappy with his playing time.
Crawford publicly expressed his displeasure at playing a reduced role in December, per that report:
"'The minutes were discussed,' Crawford said then, when he was averaging 17.7 minutes per game. 'But 17 minutes were not discussed.'
"When asked if he saw any advantages to playing shorter minutes, an implication that the elder statesman could keep his legs fresh for the long haul of the season, Crawford said, 'No. I don't see advantages, to be honest with you.'"
As Krawczynski noted, Crawford met with head coach Tom Thibodeau, and his minutes were ultimately increased, but "Thibodeau's use of the bench remained a point of contention in the locker room for much of the season, with Tyus Jones, Gorgui Dieng and Nemanja Bjelica joining Crawford among those disenchanted with the short minutes."
It certainly sounds as though there may be some issues behind closed doors in Minnesota.
Add in the fact that ESPN's Zach Lowe also said on his podcast in May that superstar Karl-Anthony Towns and the Wolves were "not in a good place internally," and it appears as though something is amiss in Minnesota.
As for Crawford, 38, he averaged 10.3 points in 20.7 minutes last season, appearing in 80 contests for the Timberwolves. The three-time Sixth Man of the Year has been one of the league's most consistent bench scorers in the second half of his career while averaging double-digit points in every season since the 2002-03 campaign.
For teams seeking a veteran bench presence this offseason, he'll be a target.