Bad history. The FCC never begged anyone to take licenses. The truth is that FM hit a peak of over 1000 stations in 1950, but faded to around 700 by 1960. Many of the independent FMs had closed, and quite a few of the AM/FM combos had either closed the FM or started simulcasting.
Established broadcasters had been very interested in FM in the late 40's and into the early 50's. They built many, many FM sister stations, and all of them failed to generate revenue with independent formats.
Much of the issue with FM in the 50's had to do with the patent and personality battles with RCA. And the lack of AFC circuitry for receivers, making them notably unstable.
Commercial FMs tried all sorts of things, such as a significant group of stations doing "buscasting" through deals with local transit companies.
Pacifica simply applied for cancelled licenses or new ones. There were plenty to be had, and there were very low costs to get a basic FM licensed.