Probably a mix of reasons, but I'd assume a big one is that no matter how ridiculous the claim is, there'll always be someone that takes it and posts it around as truth. Just look at how many people still legitimately believe he's a pedophile terrorist still living in Florida out of his mom's basement and whatever else.
There's also that whole "Greta showing up to his mom's house with a knife" thing. And tbh I'd think that anyone even remotely sane would have their patience wearing real thin if everyone kept saying you actually crave the feminine penis/axe wound smegma; joke or not. That would be insulting in pretty much every way possible, and after literal years the "joke" would be pretty stale.
