"You won't believe who loves smoothies made of bug guts" would be clickbait. 'Mildly curious fact' is just a mildly curious fact like EO Wilson telling you how much all ants weigh in a nature documentary.
Clickbait is over-sensationalising a title to bring more traffic to the article page, where ads and other monetising things can be served.
HN has been going bonkers over complaining about clickbait titles recently... it seems our denizens have somehow developed a highly-tuned sense of what clickbait looks like... but for some reason still can't resist clicking on it when they see it.
I don't think this is recent but I'm glad people do it. If I read a title that seem shocking, I'm more likely to see that's it's true or have one of the first comments call it out upon quick glance.
Edit: I don't know if I know what click bait means.