You know how some crazy people believe in wild conspiracies about chemtrails, fake moon-landings, lizardmen or flat earth.
In many of these there are large groups of people that are in the know, but don't tell the public. And only the few "illuminated" (conspiracy theorists) know and share the secrets. It creates an "Us" vs "Them" that helps to increase group-cohesion.
There are also occasionally secret government programs such as MKUltra, COINTELPRO or NSA's PRISM that are rumored around before they are confirmed by other means.

On the other side there are conspiracies nearly everyone knows about and still does not tell those who do not know. It is about made-up Santa-Claus, the tooth-fairy and easter-bunny along with a bunch of more obviously fictional leprechauns, elves and trolls.
Parents like to pretend that these are real for as long as possible. But in doing so, they make it all the more believable that a group of people can keep such a secret under covers for years.

I am contemplating to turn around and "spread the truth" about Santa and his friends. For a better future of our society.