1. it gives people agency to not freak out because they can be proactive about something. the reason nuclear energy is a boogieman is that you can't see it and it can kill you and there's is little you can do as an individual to protect yourself against it.
2. they truly didn't know how the spread of the disease is since it was a novel virus. you do however know that the lipid barrier of it makes it susceptible to soap and 70% isopropyl alcohol.
3. saying "there is no evidence that masks are effective" is true in the scientific sense. they didn't do studies so to talk about the effectiveness would have been backwards (also considering at the time they didn't know if it would actually increase the spread due to touching/collection/whatever) scientific illiteracy is a problem. the words and processes have precise meanings and those ignorant to it will glom onto certain words out of context and use that as evidence for their conspiracy theories. (see isolation of the virus et al)