I am managing not to speak ill of the dead here for which I hope to receive consideration in the world to come. But Limbaugh made an outrageous claim once that as far as I can tell was the petrified truth. He claimed that he saved AM radio. I think he did. Controversial talk radio gave AM popular content that did not depend on audio fidelity but did benefit from propagation after dark. In this area, at least, FM had the disadvantage.