People mostly seem to like KDE Plasma more than GNOME, but Ubuntu still seems way more popular. Will Kubuntu ever overtake Ubuntu? Will people ever default to saying Kubuntu instead of saying Ubuntu even when speaking generally about *buntus?
Same questions for other distros like Fedora/Fedora KDE
except during the period when they used https://en.wikipedia.org/wiki/Unity_(user_interface)
Well, they try things time to time. They had their own init system, own display server. They eventually went with more mainstream variants, almost every time.