It's quite entertaining reading about all the societies Benjamin Franklin was a part of. I recently visited the Hellfire caves in Buckinghamshire, England, where the Hellfire club (a blue-blooded social club for the wealthy and powerful) held debaucheristic Greco-Roman style banquets in what was effectively an old chalk cave. Franklin was a frequent quest to such dinners from what I was told. It's very eyrie inside, but well worth the visit if you're in the area. I know OPs article dismisses any occult reasons for the skeletons, but Franklin's associations really do lend a certain uncertainty.
If you're interested in the Hellfire club, you can read both the Wikipedia article, and a more sensationalist article below: https://en.wikipedia.org/wiki/Hellfire_Club https://www.fodors.com/world/europe/england/experiences/news...