The actual premise of Big Thunder Mountain Railroad is that an old west town of gold miners built their town on a cursed Indian burial ground and now the spirits of nature are haunting the village, which drove out the miners from the area and has resulted in an insane haunted mine train that's possessed by ghosts. I know that sounds insane, but it's the actual premise.

I like in Disneyland Paris they tied Thunder Mountain in with Phantom Manor - that many of the ghosts in Phantom Manor are the ghosts of people from the Big Thunder village who died, and part of the backstory involves some big mining tycoon whose business was ruined by the nature spirits destroying the mining town?

Did you watch the Big Thunder pilot? The whole thing felt off and unfinished but that could be just the nature of the leak (such as what the potential advertisers saw was probably more refined).

I think they eventually took the story and turned it into a comic book. Disney had Marvel make a few comics based on rides and other theme park IP like Figment.