The people who created and executed these studies wanted to save lives. They created a method they thought would be most likely to work, and time and time again they didn’t. Different dosages, different timing, different places. No benefit.
The fact that people aren’t running more studies is not because there is a global conspiracy. It’s because the drug doesn’t do anything and researchers don’t want to waste their time and their patients lives satisfying critics who don’t care about the science.
Does HCQ work if you have some magic combination of zinc? Maybe. Is that more likely than another treatment given that HCQ has been heavily studied and shown no benefit and zinc had been heavily studied for a lot of things and shown no magical properties? Probably not. So researchers spend their time on things more likely to work.