Let's not confuse the sudden popularity of folk with the media and its long time existance as "porch or kitchen music." It was around long before it became commercially popular. My guess is that it became popular because the media types were looking for something new and novel (at least to them) and it was good music, even after the subtle kinds of censorship ("hey, it's a family show") tinkered with it. Who gets the blame or the credit for the great "revival" depends pretty much on who each of us remembers as the performer(s) who opened our eyes and ears to the material. I have always felt that the Clancey Brothers & Tomm Makem were a prominant part it all.