Guns are effective against viruses in vitro; lots of things are. In vitro doesn't tell you as much as you think it does. What it tells you is that if the medication could get to the right place, in the right concentration in the right amount of time to still be relevant, with doses that aren't dangerous and none of the other tens of thousands of substances in the body inhibits the effect, it might be effective.

There is no substitute for testing these things in vivo, and most medicines tested in vivo fail even if they showed some effect in vitro.

With COVID-19 in particular it is known that there is a viral replication phase and an inflammationary phase. Giving HCQ 14 days after infection, when vulnerable people start to get put in respirators is entirely meaningless. There is no virus left; there is only dead virus particles and an overactive immune system going scorched earth. That's when they give steroids to weaken the immune systems hyperinflammatory response; which would be bad if there still was a lot of live virus. Giving HCQ early in the onset, before you end up in a hospital; when you do not yet know if you're going to be severely affected; is what could have a large effect on reducing viral growt. That requires you to proactively give HCQ. Most studies in vivo focused on giving very excessive doses (far larger than is used as profylaxis against malaria) and usually without zinc and azithromycin; and they gave those doses to people who had little or no virus left.

What that's going to do is give you a mess of studies that show different things, because they are actually testing different doses in different stages of the disease combined with different things (some give zinc, some don't).