It has demonstrable antibacterial properties, but not so much antiviral as far as I can tell. But it has a strong following, especially since all the COVID hysteria destroyed so many lives.
People take the stuff and then attribute all good experience with it. If they don't get COVID, it must be the CS working. If they get COVID and recover, the CS protected them. The confirmation bias is unassailable.
Years ago I had a recurring stomach infection. Spent some time in the hospital, went through countless testing only to be prescribed antidepressants because... because if the docs know know what it is, it must be in my head. Anyway, I took CS daily for a couple of weeks out of desperation, and the infection went away.
Maybe it was the CS, maybe not. Once I felt better, though, I stopped taking it. Many continue taking it, though, even if it doesn't cure them.