The story of the jilted woman could have roots in the island's past social fabric. Maybe there were real heartbreaks and sad tales of love gone wrong in the island's community in the past, and over time, these stories got embellished and turned into ghost stories. Also, the isolation of the island might have contributed to the spread and evolution of such stories as people had fewer distractions and more time to tell and retell these tales.
The phantom lighthouse keeper story could have come from the importance of lighthouses in the island's maritime history. Lighthouse keepers had a tough and often lonely job. If something bad happened to a keeper, like an accident or a sudden death, it could have given rise to the idea of his ghost remaining. And as generations passed, the story became a part of the island's spooky folklore.
Some of the ghost stories might have originated from the island's history of shipwrecks. The many ships that crashed on the shores over the years could have led to the creation of stories about the lost souls of sailors haunting the area. For example, the story of the shipwrecked sailor might be based on real tragedies that happened.