Why Do The Cavs Even Do This?
The answer's pretty simple: to be under the second apron cap. If Cavs wish to retain their lineup from last season (which I think what they should do), You have to get rid of the least valuable player in your rotation, and that's Okoro.
Okoro will for sure attract many teams, he's an elite defender. But trading him to other teams mean they will take back salary, while trading him to Brooklyn doesn't need to.