Everything might make more sense if you visit their website: https://polyhaven.com/ It's not just a dumb, static file server.
EDIT: The questions below are literally explained in the article, so I'm going to give up on this thread.
I feel like we're heading into the weeds. Do you get the broader point I'm trying to make?
At a glance, it still looks like mostly a highly cached static website + search. Its not exactly a high complexity backend.
Things are always more complex at scale, so there's probably more to it then what appears at first glance, but its not obvious what that is.
