This reminds me of a weird viral set of lies that circulated before the UK election in 2019.
https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.theguardian.com%2Fmedia%2F2019%2Fdec%2F10%2Fwoman-says-account-hacked-to-post-fake-story-about-hospital-boy
The initial lie was just some random person making stuff up. But 1000s of people repeated the lie by copy/pasting the text. Hundreds of thousands retweeted it. The lie went viral. No amount of fact checking made any difference and it became an election issue.
The only explanation I can think of is that huge numbers of people actively prefer stories that match their political preferences and if reality won't provide the facts to support these stories, they will happily accept fiction and righteously lie in order to support those political preferences.