I first heard of these reading Joel Chandler Harris' Uncle Remus stories. He called them "Wull-er-de-Wust" [1].

[1] https://www.gutenberg.org/files/24430/24430-h/24430-h.htm#V

Oh good, here I was thinking they could only be explained by magic.

Can we reflect on that this article starts with an Italian researcher named Luigi wearing a vacuum to try to suck in ghosts/will-o-the-wisps.

science has advanced so far now that it has invented magic

It's interesting to me how common will o the wisp was in the past, but the concept seems completely forgotten. Of my grandmother's generation and in her town (which was nowhere near a swamp), everyone reported seeing weird lights floating around during their youth to early adulthood. They were always very clear that the lights were not fireflies, which were also common at the time but very distinct. I'm lucky I at least got to witness fireflies in my youth.

Anyways, an interesting nugget is buried in that article. It says that a reason will o the wisp may have been common in the past is because lantern flames may have ignited the gas, which seems like a decent explanation. People use electric light everywhere now.

I guess another issue could be that there's so much ambient lighting from street lights and light being reflected off clouds that it's simply too bright for us to see anything. People back in the day probably experienced a lot more completely black nights.

It's completely possible that will o the wisp will be a completely forgotten phenomenon in a couple more decades, since I don't know anyone under 80 who's reported seeing it, and kids probably don't even know of it now. And it makes me wonder if there are other phenomenons that ancient people were very aware of but no living person has ever seen.