I think the reason AM radio is right wing is it’s only good for talking, and the people who listen to long conversations as their form of media consumption tend to be conservatives.

Mostly consolidation of ownership. Don't get me wrong, the fairness doctrine and played a small part. But single ownership of a vast swath of stations did far more damage than lack of fairness doctrine.

Not to mention how fair was the fairness doctrine? Did it truly serve a purpose giving voice to other opinions etc? Or was it largely limited to the same few mainstream ones? Socialist, social democrats, anarchists, communists?

Fox News was conceived in the 1970s. Yes, it started after the fairness doctrine was ended. The fairness doctrine never applied to it in any way however. Even then in the late '90s early 2000s, much of the content was designed with the concept of the fairness doctrine in mind. Any overtly political show, such as Hanity and Colmes. Already had a fake diverse/alternate voice built in. The fairness doctrine was always toothless and easily bypassable

Rush Limbaugh as problematic as he was. Was largely pushed by large conservative owned radio networks. There is some correlation between the end of the fairness doctrine and Limbaugh's national syndication. But no clear causation. No part of the fairness doctrine would have impacted syndication. And his show exist fine before and after.

Plenty of people nostalgically lament the loss of the fairness doctrine. But none can actually explain how it would help. Don't get me wrong. I'm a big fan of the concept. But the problem is, who is the arbiter of what is "fair". Or when it is fair. It makes a difference.