It's not really an acronym, just an abbreviation. "Coronavirus disease" is only two words. You could write CoviD I guess, but that looks dumb.

I'd think that it isn't a proper noun and shouldn't be capitalized at all, but maybe that's why they're the professionals and I'm just some guy on the internet.

It’s one of those things where it has become a word in and of itself because so many people use it that way