MSNBC is reporting that the short runway was lit by runway edge lights, though it usually was not (new installation?).
No excuse, but might explain why a hurrying crew in the dark and rain might have just turned left onto the first lit runway they saw....
I used to fly RJ's into KLEX for ASA, and I know many Comair pilots. Trust me, this is no slip-shod operation. If it can happen at Comair, it can happen anywhere.