Regarding specialty shows, this could be considered somewhat ancient history now, but back when there were a lot of independently owned and managed stations, you had more chances for the Dr. Dementos and those with truly unique or eclectic programming to be picked up by a number of stations.
It depends. I just read where Stryker just got his syndicated show picked up by a bunch of iHeart alternative stations because he now works for iHeart's KYSR. So sometimes being part of a big company means you get a group clearance.
But from what I see, the problem with eclectic programming isn't the ownership, but the programming. Demento was a great show in the 80s when stations played parody songs like Weird Al Yankovic and similar stuff. That pretty much went out of style in the 90s.