Cumulus was trying to pay off some debt. They needed to sell the biggest signals. For example, in NYC, they could have sold the inferior 103.9 WNBM, but they sold 95.5 WPLJ. NY area signals don't get much better than that. So, in Atlanta, they chose to tell one of their big signals.
They did not "have" to sell those particular stations, but each has a logical reasong:
WPLJ is a stand-alone FM (103.9 is a suburban station and does not count) in a market where the big players are in clusters.
WYAY is a rimshot and not a full market signal. It is a Gainsville station, not a true Atlanta one.
Even the DC station, although recently on a ratings climb, is a stand-alone music FM in a market where clusters of many stations dominate.
In other words, they were selling stations that were inferior signals (WNSH, WYAY) or under-performers that were not in big clusters (WPLJ, WRQX).
The suburban class A that is 103.9 will be a separate issue. It has little billing and just about zero ratings.