If I'm figuring this correctly, consider it just another minor log in the shitstorm (think about it) that is the Bulls financial situation.
As brought up in the comments (by 'Bullsfan7210'), part of the fallout of the league handling their books during the moratorium was a bump in maximum salaries. Derrick Rose had an assumed salary, but with the caveat that it could be raised if this happened, and it seemingly has: he now goes from $15,506,632 to $16,402,500.
Not a huge increase, but this is a Bulls team that's definitely working within the margins. If you assume they don't match Asik, pay Korver's $500k buyout, and have the remaining 3 roster spots filled by rookies, that gets them within $100k of the luxury tax threshold. Merely signing one veteran to the (2-year) minimum instead of a rookie (as in: instead of Patrick Beverly) puts them over, though they'd be back under if they get a team to take Korver. And they'd also have the entire season to try and get back under via trade.
This news, and the 'Rose Rule' in general, really gave the Bulls some bad 'luck' in terms of how the new CBA values young MVPs. But Rose (whose rehab is coming along rehab-y) is still likely underpaid and was severely underpaid during his rookie contract, so it's tough to feel too jilted here.