No. No conspiracy about AM. Rush is on FM in my locale and sounds much better than AM, which is why listeners have been migrating to FM since the 70s. It is called the market - you may have heard of it.
Well I was joking about the conspiracy, but the market does work differently in different places - Rush was on AM in Philly for years, then went to FM for a bit, and a few years back went back to AM - the major talk radio stations in the area are still mainly AM, including those carrying Prager and Mark Levin, with FM going mainly for continuous music, primarily rock and rap but some classical carried by the university stations - that’s how the market is working in this region.....
A few years ago, Rush disappeared from the local AM outlet where he had been for years, and he popped up on an FM station. He sounded awful, the victim of overzealous digital processing. His voice was barely recognizable. I don't know what his ratings were on that FM station, but that didn't last long, and now he's back where he belongs, and courtesy of Ancient Modulation, he sounds like himself again.