A lot of gamers want better performance, so a performance oriented distro with gaming quality of life features fills that gap. And ultimately there are a lot of YouTube channels promoting it and it kind of turned into a cool distro to use. This might explain the phenomenon.

I've been using it for a while now, and it's genuinely so good. Before this I was using EndeavourOS which was also a great distro, but I realized that I was basically putting in work to do things CachyOS does out of the box, so I switched and it's been great.

they offer some optimisations to the kernel and the packages that are supposed to yield a tiny bit better performance.

an incredibly small thing that rubs me the wrong way more than it probably should about their setup is that they set Plasma animation speeds to much higher values than the stock Plasma desktop uses. sure, it could be just a part of their customisation tweaks the same way using fish as the default shell is, but it feels like a cheap trick to reel in the "I installed it on my desktop and it's soooo much snappier" review kind of people. like, if your work is as good as you claim, you shouldn't need to artificially make the improvements seem bigger than they really are.

I started using linux full time about a year ago. I started with Arch, but moved to Cachy really quickly when I discovered it. All of the advantages of Arch, but repos optimised for modern hardware, and a whole heap of useful pre-configured tools, like Wine/Proton, fish, snapper etc. Arch is a bare bones, pick and configure your own setup rolling release distro. Cachy is a pre-optimised, rolling release distro with lots of useful stuff right out of the box.

I use the cachyos kernel on an otherwise plain arch setup. I don't game much, but I tried it out and just stuck with it.