Sometimes a conspiracy theory exposes a conspiracy. Sometimes the conspiracy theory is the conspiracy.
JFK assassination plots are the only conspiracy theories to be widely accepted by the general public. The moon landing filmed in a studio, the Lincoln conspiracy or the World Trade Center being blown up by lasers from outer space never gained much credence because they lacked mainstream backing. Conspiracy theories ordinarily remain on the margins. The JFK theories were too important to the liberals who were really running things to allow them to die out.