I am as right wing as you can get but I get 3 hours of Rush and then get another 3 hours of Sean Hannity doing his version of Rush's show. Hannity (and others) just repeat issue that Rush just covered for the most part.
You also don't get competition in the format because instead of competition you have segmentation. The giant consolidating media company will have one news channel, one easy listening channel, one rock channel, one talk channel, etc. and they fragment and segment the market so they don't directly compete. So ratings don't matter anymore like they used to.
Lots of things wrong with consolidation and that was some of it, as far as I can recon.
It doesn't matter. Trying to create a monopoly is like squeezing a balloon: you can grasp one part, but it just pops out somewhere else. Already there is XSIM, the sattelite radio, and internet radio. The more these guys squeeze, the more they don't expect will pop out.
And why are you just focusing on radio? It's about getting information and entertainment and our sources of that keep expanding, not contracting.
Monopoly power as you are identifying it is vastly overrated.