In talking about where folk music ended, we might look at where it started--that is,its latest resurrection after WWII. As an old folk song lover, I seem to recall that folk music was always around in some form, but it wasn't always dominant and did not become a strong force on the music scene until the nineteen fifties--maybe late fifties. Before, the scene was dominated by the crooners of popular love ballads like Bing Crosby, Frank Sinatra, etc. There were always a few lonesome folksingers out in the thirties and forties like Woody Guthrie and some of the black singers like Ledbelly (Irene Good Night). There was the English folk singer Richard Dyer Bennet whose record I happened to find in the library.
Maybe there were others, but the first folk singer that I remember becoming nationally popular after (maybe during) WWII was Burl Ives (Blue Tail Fly, etc.). For a time, he seemed to be out there by himself. But then folk songs and singers really took off after the excellent Weavers group broke the surface. Seems like after that the groups began multiply like crazy: Kingston Trio, Brothers Four, Peter, Paul, and Mary, etc.
But there was no reason to expect this style of music to dominate longer than it did. Music styles always change. I, however, was delighted when it came and greatly disappointed when it gave way to rock and roll in the seventies. Its high popularity seems to have lasted over a decade, and that's not bad.

Ron Crowe