I would attribute the rewriting of "Poor Dhrinnan" to "Paul Campbell" the pseudonym
used by the Weavers. Pete Seeger and crew had something to do with the song's reinterpretation and rewriting from Leadbelly's version.

The Weaver's album with the song on it probably charted but was more recognized from the concerts they did at Carnegie Hall.

It has been my experience that true attribution to many songs is not accurately given.
Also, arrangements of the song in question can alter the song itself and make it more acceptable commercially even when the arranger is unknown.

There are more "folk songs" (written communally) then we know.