the 'at the moment' probably explains it - a lot of online fora have, for want of a better word, fads where there is a lot of discussion of a particular topic for a brief while, then it fades and sooner or later a new topic comes along. I quite like the phenomenon personally.

People are desperate to keep "working" from home.

Someone posted an article recently. Morbidly fascinated people dig out more and post that, too. It all performs moderately well so karma hunters start doing it for the points. Eventually, the audience is saturated with prion content and the fad dies down.

There's an unexplained outbreak of a weird brain disease in Canada. People were theorising that it's a prion disease.

Prions have been posted a lot about before Corona. If I had to hazard a guess, it's because they're even more of a curio than viruses, bacteria or fungi.

I'm not so sure it is that popular on HN. I don't remember seeing any articles all that often before recently with the outbreak in Canada. I'll see the topic pop up far more often on Reddit, but it's still fairly rare. I think people are interested because it is such a terrifying thing that we don't have any good solutions for. So it inspires discussions whenever somebody reminds everybody else "so, hey, this is still a thing" and it makes its rounds.