Dr. Risch's paper points out even more studies than the one you mentioned, and to this day he says the research says hydroxychloroquine, combined with zinc and azithromycin, are incredibly effective, around 85%, like Pfizer's new drug.
The mystery to me is why, given all the observational data of h/z/a's effectiveness, not one RCT was ever performed on vulnerable patients early, like the Merck and Pfizer drugs were. It's almost like they didn't want safe, cheap, effective and already-readily-available drugs to be used...not because they were ineffective, but because they wouldn't be as profitable.