Something I was thinking about the last several days...
Could Toronto have flipped DeMar for Kawhi...only to ship him out at the deadline? Hear me out. DeMar was signed to a contract with a few more years left, right? They swept out Casey, looks like a semi-rebuild is imminent. So they get rid of DeMar's contract, take on Kawhi. They can trade Kawhi at the deadline for some young pieces or picks (particularly if he plays well) -- a bigger treasure trove than they could have gotten for DeRozen. So not only did Toronto save money by getting rid of DeRozen, they'll save more money by trading Kawhi at the deadline, and get more in return for him to help with the rebuild.
Sure, they still have Lowry on that ridiculous deal. BUT, Lowry has two more years at 31 (for 2018-2019) and 33 million (2019-2020), respectively. Kyle plays this year, and then the Raptors trade him this offseason for more assets. Not only do they get out of that bad contract (someone will take Lowry), but they'll theoretically be able to net picks and young players for both Kawhi and Lowry, and be in a better position for the future.
Thinking about it that way, I think they made a smart move, they've decided they can't truly win, and want to rebuild for the 2020-2021 season and beyond. Makes a lot of sense.