The share of Republicans and Republican-leaning independents who believe that President Joe Biden’s 2020 election win was not legitimate has ticked back up, according to a new CNN poll fielded throughout July. All told, 69% of Republicans and Republican-leaners say Biden’s win was not legitimate, up from 63% earlier this year and through last fall, even as there is no evidence of election fraud that would have altered the outcome of the contest.
This isn't so much a mystery, but more of a reaping of what was sown.
Right Wing media sources such as Breitbart and Fox News, have been nurturing many lines of thought, mostly in order to fire up the conservative base, versus providing useful information.
When you want your base to be an angry mob, and spend considerable resources to keep them angry, ill informed, but likely to vote, this is what you get.