The major conspiracy theory was that trump colluded with Russia to win the election. As far as I’m aware the Mueller report said Russia stood to benefit from a trump presidency but Trump didn’t collude.

So Trump won legitimately. Even if people voted with the wrong information. And the losing side threw its toys out of the cot.

Then when Biden won, the losing side threw its toys out of the cot.

In both cases there’s conspiracy theories. Russian collusion and rigged elections.