Well, we should say two things about Rick Sklar. First, WABC was an amazing station. As David says above, so many people listened and tried to copy the magic. I was lucky that I grew up in NJ and could see the WABC tower from my family's front window. I loved it!
Did Sklar see FM radio becoming dominant as quickly as it did? No, but I'm not sure others didn't either. Most people thought AM and FM music stations would co-exist. FM would have more adventurous formats and fewer commercials. I'm not sure what Sklar would have done differently if he had realized ALL music formats would move to FM, both mass-appeal AND more sophisticated. WABC was the nation's most popular station for many years. Then it fell off a cliff when FM radios became inexpensive for homes and easy to install in cars.
Second, Super Radio sounded great to me! I have heard that sample tape with Dan Ingram hosting. If I owned an FM station in a medium to small market, I'd subscribe! But affiliate sales were not Sklar's job. He set up a great sounding network, easy for local stations to adapt. ABC signed up affiliates but apparently not enough in large markets. The company's expectations were apparently too high. Maybe with all those talented DJs who expected to be paid well, you couldn't run it with just a lot of small to medium markets. And as said above, it was too early for stations in large markets to hand over their programming to a round-the-clock network, with only your morning show local. That's even if you could have Dan Ingram, Ron Lundy, Jay Thomas and other big names as DJs on your station, owners in large markets didn't want to give away so much control.