Because I don't commute anymore, I'm way behind in my podcasts. Three podcasts I listen to, and am behind in, are the Naked Scientists (a British popular science broadcast), and the Nature and Science podcasts (which cover weekly scientific news). The interesting thing is that, as I listen to them now, I'm going through a live view of the past with present hindsight. It's fun.
One interesting thing is that aerosol, airborne transmission of many viruses was (and is?) controversial, or at least an open research question. (Recognition of aerosol transmission of infectious agents: a commentary [Jan 2019] https://bmcinfectdis.biomedcentral.com/articles/10.1186/s128...)
Up until at least mid-April, the default belief of the medical community seems to have been that Corona viruses were not, or at least not particularly, airborne. Instead it would be spread by physical contact (contaminated surfaces, etc.) or large droplets produced by coughing or sneezing. As a result, the default use of masks was not particularly recommended.[1] (And that's before you consider the scarcity of PPE for medical users at the time.)
After about mid-April, the facts on the ground seem to change, and things like aerosol transmission and asymptomatic spreaders suddenly become a much larger concern. (And a lot of people on my podcasts got sheepish with the egg on their faces.)
As a result, it's not particularly surprising that an epidemiologist would not consider wearing a mask to be particularly useful in early March.
[1] One thing the article does not touch on is the tendency of actual experts to get feelings akin to religious hysteria based on internal fights, with the resulting dramatic statements spilling over into outside conversations. (I had this one paper ripped to shreds by a old-time network guy because I and my advisor had the temerity to consider keepalives/heartbeats.) I suspect there may be something behind the default assumption up until April that masks were bad.