Seems to me that if the "supernatural" details were not appealing, they would have fallen away from the song and left the story of "tragedy as a result of carelessness". If the tragedy is the appeal of the song, then why have other similar stories gone by the boards? It retained these qualities even in migration which is unusual. And several modern singers have chosen to sing it. A bit like the popularity of "Outlander"- throw in some "mystical" spice to a semi-historical story and you've got a hit.

best- Julia