Bucks: Why? Imo Derozan is a better version of Middleton right now. He's the best slasher and has the better midrange. Demar averages a 3 pointer a game and Middleton only averages 1.7 threes a game I don't think this move damages the spacing at all. Demar is also the better passer, ball handler, and defender than Middleton now.
DeRozan: 22/4/5/1 on 47/34/85 Drating 117. Orating 121
Middleton: 15/4/5/1 on 49/47/83 Drating 116 (while usually playing in lineups with Giannis and Lopez... worst out of the starting 5) Orating 124
Bulls: Basically they make sure that Demar doesn't leave for nothing and get a high 2nd round pick back and a movable contract.