My guess is that kde is more “familiar” for gamers coming from windows… It looks more like windows than gnome
Fair enough, though Gnome does resemble mobile interfaces like the ones in Android (at least I think so, I’m going to get grilled for this aren’t I?), which would make more sense in what essentially is a mobile device that should have mobile touch based navigation due to lack of physical keyboard and a proper mouse.
KDE may look like windows but it also functions way worse than Windows on a touch screen device, at least most windows devices have a keyboard and mouse but the SteamDeck requires you to use an external one, which may or may not be available.