Mild Conspiracy Belief Signals Vigilance

Because people are really more concerned with the world immediately around them — which genuinely contains many conspiracies (cheating partners, infidelity, selling junk) — believing and talking about conspiracy theories about the larger world is a direct signal to those around you that you're watching and won't be fooled, which is socially functional; it only becomes pathological when taken too far, and conspiracy believers cluster (believing one tends to mean believing many), revealing the underlying signal isn't really about the specific claim.