As others have mentioned and alluded to, The Drive is terrible and they can't even fill 3 hours with solid content, I'm not sure how they think they're going to fill 4 hours each and every day and generate decent ratings.
So I guess the references from the current on-air talent about how there were options in the works for replacing M&A fell through. They must have been scrambling to figure out how to re-work the lineup. iHeart probably told them they couldn't hire replacements, or maybe they just couldn't pay enough to bring in anyone worthwhile.