Why the Knicks do it: There have been rumors circulating that the locker room is unhappy with KAT. This clears him out and adds Collins to the starting lineup who can still be a stretch big while Robinson anchors the defense down low. This also gives them more depth in Clarkson and Sensabaugh off the bench. With the 21st pick, the Knicks could pick up a backup big like Asa Newell or Collin Murray-Boyles to back up the bench depth.
Why the Jazz do it: With a change in the front office and the claim that they are not going to tank anymore, the Jazz need a number 1 option right away to stick to that narrative. They need to move off of Collins and Clarkson's contracts. This will give them KAT as their primary scorer, with most likely either Tre Johnson or Ace Bailey as the number two guy and Larui Markkanen as the number 3 option and Collier as the facilitator. Kessler would anchor the defense down low. This wouldn't make the Jazz immediate contenders but would make them competitive right away. Would also allow the younger guys that they are developing to still get reps as the rotation pieces off the bench.
