Sigh. An interesting study, but such a ridiculous prediction. The authors estimated the relative risk of wearing a mask to not based on studies mostly conducted in healthcare workers during SARS/MERS, and then extrapolated this directly to the US
https://twitter.com/JWatch/status/1324441354378780672
In fact, the reduction in deaths that's cited here as the main outcome is a direct result of the relative risk (0.65) that the authors found for mask-use compared to no mask-use when aggregating together studies on masks 
So, they predict 500k deaths in the US by Feb 2021, but if 95% of people wear masks in public, this goes down by just under 35%
But is this reasonable? The study uses the results from two previous systematic reviews that almost exclusively looked at data from SARS and MERS for mask-wearing. Are studies like the below ones reflective of the risk of transmission for people in public for COVID-19?
Even if we accept that, on average, face masks will prevent 35% of infections in healthcare professionals from MERS/SARS and influenza, what in the world does that mean for COVID-19?
Given that the main result is a direct consequence of this assumption for mask-wearing, I think it's worth noting how flimsy the evidence is!
Anyway, I suspect that 95% mask-wearing in public would have a relatively small impact on the eventual death toll from COVID-19 given that most transmission happens in non-public places such as workplaces, schools, universities, and at home
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