My limited understanding is that the immune system works better at fighting off a new virus based on how similar it was to a virus it has already fought off in the past (or vaccinated against).
So maybe exposure to other coronaviruses reduces the severity of a cv-19 infection?
That’s what I think, too. Supposedly, from my very limited reading, they are trying to repurpose drugs to do that. But if they continue to take their sweet time about it, there won’t be an economy to mass produce it when they finally find it—IF they find it, as the finger-waggers tell us.