If Fallout is a universe that has Aliens, why cant we have ghost or even possessed people?
One thing that people get caught up with is the past. People will say "no that is not Fallout Lore!"
What people dont realize is that Bethesda now owns Fallout and they are now the creators of Lore. They could expand on how power armor works, or create new factions, True factions that rival the iconic Brotherhood of Steel or the Enclave one they can call their own. Or even add things like supernatural aspects but still feels believable in this world.
In Skyrim people fear monsters. In Fallout people could fear ghost and demons. Imagine being locked in a vault with a possessed person where the lights are flickering or just feels haunted.
I am aware that there is something in the game about Salem, but I havent played that quest yet. I'm hoping for something along the lines of things that we wouldnt expect but freaks us out and make us more terrified of the wasteland.