Looks like there was a schedule change on the CVG-MKE flight (4079) from a 9:25AM departure to a 11:10AM departure. You could probably get your original flights back, but you'd have a 4+ hour layover in CVG. The 4+ hour layover is probably what triggered the re-route through MSP. There are a number options that are more closely timed to your original flights.

There's an 11:55PM red-eye flight (2216) to DTW on 29Apr that you can connect to flight 2356 to MKE on 30Apr. This will get you into MKE at 8:58AM on 30Apr. I'd ask for those flights. You are entitled to a free change or a full refund (however, DL will not pay for your hotel room, car rental, etc. should you choose to keep your current flights).