What do you need to run a network? A Director who knows what he is doing.
Compelling content. Good engineering with the proper resources. Management that has trust the content, director and engineer.
This existed under CBS.
Entercom/Audacy chased all those people off.
The CBS stations were not a "network". For all practical effects, networks died in the U.S. between the early 50's (lift of the TV licensing freeze) and the mid 60's. By 1970, all that was left of the old, traditional webs was mostly news services and a couple of dead or dying shows.
After that, the networks that remained were developed around concepts like a sports team or area / regional agriculture. By the end of the 60's, we had the creation of syndicated shows like American Top 40 and King Biscuit Flower Hour that were on a "station in every market" and lots of sports.
And then we got syndication... Rush, Bobby Bones, Charlemagne and the like. A station could have a different show from a different network in every hour or daypart. Networks were based on shows, not shows based on the network such as in the days of Red, Blue and NBC.
The only really successful full "networks" today are the religious groups that use the K-Love model or NPR. In the case of NPR, all kinds of local stations are built around the NPR offerings, with each one being as different as fingerprints.
Today's successful networks seem to have one thing in common: they are non-commercial.
Yet in much of the rest of the world where commercial radio exists, there are "national services" which are are the same programming carried on dozens or hundreds of transmitters covering a whole nation. That works, and where this is done, stations and station groups are not standing in line to file for bankruptcy.
But nobody owns a station in every one of the top 250 markets or so. They may have 8 station in one, and none in another. The whole concept of a single program format being on transmitters "everywhere" is not part of the American licensing, operations and programming model.