Giacomo Siffredi said:
By the time the NBC News and Information Service (NIS) was launched over WNWS 97.1FM in 1975, Several NYC FMs had already developed significant audiences, including WNEW-FM. Had NBC's news format been successful, it would have developed traction. Even if not on a national level, it could have continued locally.
Among all news listeners, who are, for the most part, over 35 or even over 40, FM was not dominant in 1975. It was not even close to parity. 12+ parity, nationally, came several years later but it took longer for FM to be dominant, especially in the older demos.
Further, NIS was not successful because it was neither local nor as good as it had to be to be successful. Most NIS stations were AM, and the AMs were not successful, either. So the issue there is not even an FM matter... it was one of whether the NIS product was any good.
Oh, and using WNEW FM as an example makes little sense... album rock was predominantly an 18 34 thing and does not reflect any FM potential that news might or might not have had. And since all news is a costly format, going it "solo" when NIS died was not an option because the format, with few exceptions, was a Top 10 market proposition only.
And while WEPN-FM cannot be measured by audience alone, as you correctly point out, $12 million a year, even for ESPN, is a lot of money to spend on simply "branding".
But the success of ESPN is all about branding and brand extensions. If you look at Disney's gross revenues, you can see that $12 million is pocket change.
They already had that with 1050 AM before they LMA'd 98.7FM. They realize the potential for more younger listeners is with an FM signal.
Sports does fine in younger demos on AM. The issue with 1050 is the night signal, and since "night" begins in the middle of PM drive in the winter months and ends well into AM drive as well, it was critical to get a better signal... and being on FM in the long run is going to be an advantage.
However, it is an impending debacle because its ratings, so far, have tanked when contrasted with its predecessor format, WRKS 98.7 Kiss FM.
The Disney folks could care less what WRKS had, ratings wise. They were looking for a signal, not a format. Right now, the men 25-54 share is in the same "ballpark" as the 25-54 men number for WCBS and WINS... they don't look dismal as you suggest.
You forgot WIP Philadelphia whose 610 AM simulcast at 94.1FM, now WIP-FM Philadelphia, displaced heritage rocker WYSP

And that's another example of an FM spoken word format that has been near bottom feeding the PPMs recently...
There are very few such examples. The successes far, far outnumber the setbacks. And, in the majority of the unsuccessful situations, it has been because a relatively poor performing AM has added or moved to FM, where it simply becomes an underperforming FM... such as WMAL.