They don't support really old hardware which enables to ship better optimized packages by default and other performance boosts at expense of non-gamers. I have noticed multiple times that a package I wanted was not available in classic arch repos but was in Cachy's. As far as I know it's not that different from EndeavourOS (not that I've tried it). To me it really just seems like a distro that suits ME, a bit lazy tech savvy gamer, the best and there is not any visible dirt.

It arrived at the right time with the right promises.

It came up during the SteamOS craze where a lot of people were looking to switch over to Linux, but wanted something easy.

• SteamOS was not yet released for anything but the Steam Deck
• It has an easy installer and good GUI tooling
• It comes with KDE & gaming optimizations, so it's easy to use for people coming from Windows with no fiddling
• It's not immutable, so you can actually use your PC for anything, not just gaming
• It has an Arch base and still uses arch repos (apart from their own custom packages), so it's also familiar to people already using Linux

Unlike other distros, it doesn't have anti-features, and doesn't sacrifice anything for the sake of ease-of-use, while providing a very smooth experience (and welcoming to people who never used Linux).

And it came out at the perfect time - it wasn't an old thing you had to persuade people was "good all along"; it's a purpose-built distro made to answer the specific use case people were seeking when leaving Windows, at the exact time articles & youtube videos were hammering on Windows & Linux gaming was a huge topic of discussion.