I'm not sure if awareness of the dangers of UV damage serves an explanation. The area covered isn't huge and tights aren't typical regions for skin cancer. Having said that, the heightened awareness may introduce a cultural bias…

I guess speaking of cultural bias, one other thing to note is that Europe and the US are not the only game in town anymore.

Japan and Korea, and probably in the future China, are big players in cosmetics and fashion these days, and those countries never had a big nudist culture and generally dislike tanning and nudity even more so. And their products are gaining ever greater market share in the West.

Of course. I was writing mostly from a European perspective.

Right, but even young European influencers today are often hawking Japanese and Korean cosmetics.

Our cultures are mixing together in this globalized world, and other stuff like K-pop is already big business in Europe.

My recollection is that Speedos weren't exactly rare but they tended to be more associated with sports than something you wore to hang out at the beach.

There may be cultural differences (esp. regarding the US, which were generally known as somewhat prudish in these concerns), but in Europe sporty swimwear (rather by Adidas and similar domestic brands than real Speedos) was the default. Anything else was asking for an explanation or would even provoke open ridicule (like Hawaiian shorts).

That is almost certainly fair. I know I wore Speedo-like swimwear for water polo but would have worn nylon shorts of some sort at the beach generally.