Don't blame Clear Channel (at least here in the States). Put the blame where it belongs: blame Congress and President Clinton for the Deregulation Act of 1996. That's what started it all.
I worked in the radio industry back then. I remember all the talk, all the news of radio mergers and buyouts.... it was all over the industry magazines -- it was a regular buying frenzy. Big radio companies buying out other smaller companies, merging like crazy, then doing their IPO and going public on Wall Street -- individual stations became parts of 'clusters' and with consolidated facilities, and then people were let go.
When one company bought another company, the new bosses would lay off people to either cut costs outright -- or they would lay off people because they already had people in another cluster that (thanks to computer networking) could handle the extra workload. Or they already had a division that handled that particular radio service (be it production, voice-tracking, programming, etc.), and they didn't need the redundancy.
It all started about the time of the dot com boom, and had the same kind of greed driving it: get those stock prices up, cut costs, buy another company or merge to try to make the stock look more valuable.
Over the next ten years maybe 50,000 radio personnel lost their jobs. Those jobs ain't ever coming back. Of course, de-reg isn't the only reason for the loss of those jobs. The internet, technology advances, and falling listenership all contributed to it... but deregulation was probably the biggest factor in the consolidation and homogenization of radio in the U.S.