Some of the more famous conspiracies are the base to many of the anti-government groups. They feed on the gullibility of people who aren’t happy with their lives. They look for something to help them believe some elite secret group is running their government and hurting them somehow.
Republicans hated Franklin Roosevelt so they concocted a story that FDR forced the Japanese to attack us at Pearl Harbor. FDR was supposed to have kept the admirals and generals from knowing the attack was coming. History shows General Stark and Admiral Kinner were told to prepare for an attack a month before though the war games thought the Philippines was the most probable target. The November 30th Honolulu newspaper stated an attack was imminent. Millions believed the “Big Lie”.
Another long lasting conspiracy is JFK was actually shot from the grassy knoll by either Hoover’s FBI or the CIA. In lieu of those two government agencies the oil execs in collusion with the Russians or Cubans paid Oswald and Ruby to kill Oswald. LBJ was another possible conspirator.
Every decade seems to have another conspiracy to help gullible people find some solace for their alternate reality. Trump’s “Big Lie” about the 2020 election may be the main one for this decade. It has been disproved by Republican Governors and many audits conducted by Trump biased groups. Even Trump’s front people deny any mistakes when under oath. Still, gullible people want to believe the lies.