Early laboratory research indicated that ivermectin could kill the SARS-CoV-2 virus, but this was later found to require, in many cases, toxic doses far exceeding those approved for humans. Antivaxxers latched onto this and ran with it, spreading the misinformation far and wide.

Having worms is common in poorer parts of the world and deworming humans is quite common. I imagine it's made its way through immigrant communities and then white people latched on.

Something else white people stole 🤣

Much like every culture war issue the right grabs onto: there's no logical basis for it. It became an in-group thing to signal to others that you're "one of the good ones". Sane people pointed out how bad it was which only made ivermectin more entrenched as THE healthy thing like crystals, red light therapy, essential oils, basically anything not backed up by a healthcare expert.

I think its just people that can't tell memes from facts.