Why is the ballad Flannan Isle tragic?

The Ballad "Flannan Isle" is tragic because it tells the story of three lighthouse keepers who mysteriously disappeared without a trace from the remote island. The eerie and atmospheric lyrics paint a haunting picture of the events that transpired, leaving the fate of the keepers unknown and shrouded in mystery. The sense of loss and unanswered questions in the ballad contribute to its tragic tone.