Because Chicago (not a div opponent but i assume you meant conference) is making this trade for financial reasons rather than competitive reasons (at least on the surface). We aren't giving them cap space that they can use to sign a major free agent. At best it'll give them enough cap space to use the full MLE. We help out their pocketbooks they help our roster. For us as Toronto fans, that's a win. If we can get a draft pick out of it (preferably that Charlotte protected), even better.
If we've got ownership willing to spend into the tax, we can use that to our advantage to acquire guys who are talented but overpaid, and then retain those guys under bird rights in the new, fiscally tighter nba. There's a rare window right now to execute that strategy. I'm not saying it's a great strategy, but I can see the logic in it.