It's not a special case at all. 20 years ago this was standard architecture (hell, HN still caches static versions of pages for logged-out users).
No, what changed is the industry devolved into over-reliance on mountains of 'frameworks' and other garbage that no one person fully understands how it all works.
Things have gotten worse, not better.
The "this won't scale" dogma pushed by cloud providers via frameworks has actually scared people into believing they really need a lot more resources than they actually do to display information on the web.
It's really dumbfounding that most devs fell for it even as raw computing power has gotten drastically cheaper.
I was having a conversation with some younger devs about hosting websites for our photography hobbies. One was convinced hosting the photos on your own domain would bankrupt you in bandwidth costs. It's wild.
I very much enjoyed the Vercel fanboys posting their enormous bills on Twitter, and then daring people to explain how they could possibly run it on, you know, a server for anything close to the price.
I took the bait once and analyzed a $5000 bill. IIRC, it worked out to about the compute provided by an RPi 4. “OK, but what about when your site explodes in popularity?” “I dunno, take the other $4900 and buy more RPis?”
Sounds like the real web scale was all of the AWS bills we paid along the way
Static HTML and caching aren't special cases by any means, but a message board where literally nothing changes between users certainly seems like a special case, even twenty years ago. You don't need that in order to make a site run fast, of course, but that limitation certainly simplifies things.