It actually is something of a wonder drug

And it worked wonders on COVID patients who actually had parasites in the "throw everything at the wall" period. Word got out some patients had improved because of it. It became a whole thing because doctors didn't got the same results with ivermectin in others trials, probably because their patients didn't have parasites, and ruled it out as the COVID cure. Arm chair viral experts refused to believe it and made it a conspiracy, and from there on became a cornerstone of anti vax and right wing politics. Of course right wing commentators now make it the cure for cancer.