Classic (but not too classic) Country works only in markets where there is already a lot of country listening. Cumulus Country Icon WSM-FM is usually the top country outlet in Nashville. Other strong Classic Country stations are in Tulsa and Oklahoma City. But Chicago isn't such an animal. A Classic Country station in Chicago would be trying to build its success on the 40-54 segment of the country audience, which is already not that big.
Most of the largest U.S. markets have two country stations and a few have three. The exceptions are NYC (1), Los Angeles (1), San Diego (1), Philadelphia (1), Washington (1), Miami (1) and San Francisco (0). Even places like Boston, Detroit, Minneapolis, Seattle and Portland have two.
There are plenty of Chicago-area residents who trace their family histories to rural America. They came to Chicago a couple of generations ago to work in the factories and other blue collar jobs so their offspring might be inclined to like Country. Plus there are a lot of full-power FM signals in Chicago, more than in most cities. You gotta program them with something. So it's smart for iHeart to give Country another try before throwing in the towel.