While in the 60s roughly 77% of Americans trusted their governments, this has dramatically fallen to 19%. Governmental distrust rising means that people are increasingly inclined to believe conspiracy theories that portray the government as an evil actor. While the perpetrator of conspiracy theories used to generally be groups of people (E.g. Jewish people, the Freemasons), the government is increasingly characterised as the perpetrator of conspiracies. People who distrust the government have plenty of reasons to feel that their government could be participating in a conspiracy. Beyond this, it is easy to then continue to subscribe to conspiracy theories.
[P1] More and more people distrust the government. [P2] This naturally leads to people believing conspiracy theories about the government.