Not advocating for any service in particular (though disclaimer I do work at msft), I’m honestly wondering why someone would choose to ship a website as a server running on a hardware time slot rental with all the setup, cost, inscalability, and management that requires, as opposed to a free cdn that gives you a website with only some markdown.

Mainly because it was not a mere markdown. You can't see right now, but it had submission forms with previews and rating forms. Yes, you can route dynamic parts to elsewhere, but it was not really static for a while.