Cloudflare have successfully made their products so common people use them without giving a second thought to whether or not it makes sense
Coming back to point out cloudflare is probably the most common way of hiding your servers ip if you are running a greyzone or illegal service, and its useful for running many websites on the same VPS without reverse DNS busting you
Sure but that has nothing to do with turnstile. You turn those on when you're site is getting hammered by bots, which seems odd for that particular site.
DDOS websites get DDOSed by their competitors all the time