@freemo
It's probably closely related to media literacy and political savvy, and critical reasoning skills generally. And it has a lot to do with character and loyalty to the fundamental principles of democracy. If someone doesn't have the skills to seek out reliable sources of information and to critically analyze those sources and information, then they might make the incorrect assessment that the election was "rigged". If those people also have a strong loyalty to those fundamental principles, then they would likely be very upset.
However, if someone was able to determine the actual facts and knew that Biden won the election but they didn't have any loyalty to the fundamental principles of our republic, then they might lie about it and say it was a fraud if they thought that they had something to gain from it. But that last part, that's a different kind of delusion -- to think that one has something to gain from overthrowing a democracy. That's never true. Dictators are never satisfied and will eventually take away everyone's power and freedom. The corrupt ones who think that they can ride the back of tiger eventually lose their own freedom and power -- the hard way.
@Pat honestly if we are talking everyday people I would expect 100% are delusional. Corruption doesnt make sense, they have nothing to gain from it. Politicians on the other hand, now that would gbe interesting.