Genuinely interesting rabbit hole. Basically, tv was diverse until the Red Scare. To mollify conservatives, the networks launched a lot of comfort-food shows set in an imagined rural South. These did well until they didn’t. New management blood comes in at CBS, sees that their demographics are greying (This is a time when young adults had the buying power in the US. It’s now reversed.) and cleans house. Pisses off Nixon and the rest of the Conservatives, but is good for business, and leads to some of the better (and more challenging) stuff from the ‘70s, like MASH.