Have there been conspiracy theories that turned out to be true?
There probably is one somewhere (depending on how far you’re willing to stretch the term “conspiracy theory). But the overwhelming majority of them indeed ended up being wrong. This is not surprising, seeing as most conspiracy theories are made up based solely on an over-active imagination and the unshakable assumption that any and all professionals are always lying, with little regard for things like facts, statistics, logic, and common sense.