>This paper uncovers a very robust mechanism that explains a lot

It helps explain. This isn't the first time that impaired mucosal immunity has been identified as a root cause. Prior to this the impact of cold air was discovered to inhibit the functioning of dendritic cells, which physically sample anything strange and coordinate to other immune cells in the innate immune system to respond. These play the central role in coordinating immune response in the mucosal system, as well among their various types later responses via B cells. If they are rendered dysfunctional for several hours by cold air you can see why you would be vulnerable. Viruses ensnared by extracellular vesicle components would also be phagocytised and likely recognised by dendritic cells. The swallowed mucous then presents to payers patches in the gut to expand the response to antigens more systemically.

I can find little follow up research on this, but I remember reading about this discovery by a scientist some years ago.