And they are still testing whether ivermectin "cures" COVID rather than being a preventative. That has been commented on as well. I believe that other drug that Trump was taking in 2020 was believed to be a preventative also.
Most of the people I heard about who took ivermectin for COVID were prescribed a number of things just included ivermectin. Makes me curious if there is anything to that.
Regarding horse paste, my understanding is that a) it was touted by proponents as a treatment that helped, but was not a “cure”, and b) it was most effective when taken with zinc and possibly other vitamins/minerals. Most studies have only been concerned with whether it had direct activity against covid or was in some way a cure, and they looked at it in isolation rather than with zinc/etc supplements. It’s entirely possible it was a very helpful drug even if it didn’t do those specific things the studies looked for.
Anecdotally, ivermectin seemed to help my wife recover, and also helped my best friend’s sister avoid hospitalization. Also, the parts of Africa and India where ivermectin is consumed like candy Covid seems to have been far less impactful than other places. Proof it’s efficacious? No, but while the plural of anecdote is not data, eventually if gather enough anecdotes, and apply sound analysis to them, you can develop data.