I think the leading hypothesis is that nicotine may have a protective effect against COVID-19, which is strong enough to more than counteract the negative influ

I think the leading hypothesis is that nicotine may have a protective effect against COVID-19, which is strong enough to more than counteract the negative influence of the lung damage caused by smoking. (This would explain why former smokers are worse off, since they have residual lung damage but no protective nicotine.) Of course this is all quite hypothetical, and may turn out to be wrong, but I gather it’s biochemically plausible. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7192087/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7192087/