In principle, HCQ can be effective against some coronaviruses and not others. Ditto for masks. So I'm not convinced we knew anything specific about COVID-19 just due to prior research, but the precautionary principle suggests being overly conservative in most assumptions.

Fauci actually did mislead the public about masks, but he actually believed they were effective, so he lied to the public claiming their ineffectiveness at first due to fears of shortages.