Here's Rush's version of the story, told in 2008. Rush referred to EFM as EIB:
Thanks for finding that story. I don't frequent the Rush website, and that is a gem... well told in the earlier Rush style, too.
What is a deciding factor here that has not been mentioned in the thread is Docket 80-90. No, not the change in the Fairness Doctrine but the changes in FCC licensing application, upgrade and allocation rules that fell into place in the later years of the 1980's.
By 1989 or 1990, we started seeing many, many new FM stations which were mostly in small and medium markets. These further devalued existing AMs in those markets and made them seek shows that could run fully automated and had no cash cost. Being AMs, that meant mostly talk shows since the ability of the satellite music networks to make AMs viable was already mostly gone.
Add in the upgrades to Class A FMs, giving them greater coverage or allowing them to move to a larger market (previously such an upgrade opened on up to a cross filing; see the Bonita Springs case that triggered Docket 80-90.). Again, a change in the needs for programming.
Satellite had made real time format delivery possible by the time the 80's were well along. Up till then, syndication of formats was done via tapes sent "in the mail" and assembled by sometimes clumsy automation. Now we could have real time formats, with jocks who could talk about new songs or artist news and talk shows that discussed today's news. And, other than the equipment costs, satellite could serve Rush's 600 stations for the same cost as for the first dozen or so. No incremental costs.
Advertisers liked the ability to run real-time spots in the "network" programming as they knew when and where the spots ran; taped syndicated formats had no "real time" guarantee and the delivery and fulfillment of copy/spot changes was unreliable and had great delays due to logistics.
So Rush walked into the post Docket 80-90 world where there was cost efficient satellite delivery, real time advertiser fulfillment and scheduling, freedom from the Fairness Doctrine, a whole bunch of new FM stations that forced dying AMs to look for talk programming to survive and a radio economy where half of all stations were losing money, making barter seem oh-so-attractive.
And Rush was a former Top 40 jock. He did not come into talk radio as a journalist but as an entertainer. So he understood that he had to do a fun show. He gave his sidekick a funny name. He did sometimes goofy Top 40 music radio things, and knew when to lower the "Seriousness" voltage so as not to be boring.
Perhaps Rush was not a creative genius, but he was clever and aware.
Los Angeles is a good example, where, Rush went up against the old line KABC talents: they were studied, serious and astute. But they were, by 1990's standards, boring. In part of the 90's, KFI had David Hall as PD and he was able to build the rest of the station and even the news department around Rush and Dr Laura; this was not KGO's Ronn Owens (some called him "the Bay Area's Voice of Reason") but more of a Jay Leno or Johnny Carson who talked about current events instead of movies and comedians.