The following all made it to Top 40 airplay, and nevertheless survived to have careers as folk singers:

Dave Vank Ronk, singing Joni Mitchell's "Both Sides Now"

Pete Seeger, singing Malvina Reynold's "Little Boxes"

Arlo Guthrie, singing Steve Goodman's "City of New Orleans"

Joan Baez, singing Phil Ochs' "There but for Fortune"

Notice how they are all covers.