The election fraud claims are more recent, but this idea that conservatives somehow form the "majority" of thought in this country is a long standing belief among conservatives even as all available research shows that the majority of people in the United States lean toward liberal ideas.
Conservatives have also believed that "Conservatism cannot fail, one can only fail conservatism". People who lose are often decried as "not a real conservative" despite the absolute fact that Conservatism as an ideology serves to structure society into a hierarchical structure (a pyramid or triangle) which means that those at the very top get the majority of the benefits and power, while the base (majority) get no power and little benefit. Conservatism has always had to come up with a way to pull in enough people (within a democracy) to maintain power. Republicans have sought to severely limit voting as a result of knowing that their actual policies work for very few actual people.
The ideology is bankrupt and lacks the ability to convince people based on its merits, so they lie. They make up myths, and they use symbols and emotion to both drum up support, and discourage opposition.
This "election fraud" thing is their latest attempt to maintain an ideology that should die off.