To me, a lot of it feels like people can't believe that a thinking human would ever vote for "the bad guys", so they go searching for some other explanation. It must have been some sort of brainwashing, that's the only reason someone would ever fall for their obvious lies!
Curiously, I very rarely hear people who complain about social media admit to it influencing their own political decisions, it's always their opponents who are being led astray.