Are they so different that it’s justified to have so many different distributions? So far I guess that different package manager are the reason that divides the linux community. One may be on KDE and one on GNOME but they can use each other’s packages but usually you are bound to one manager
Because linux runs on an incredible amount of platforms with an incredible amount of hardware targets and platform goals.
It runs on every supercomputer and every raspberry pi and every android phone, as well as most web servers and almost every steamdeck.
Use cases are so dramatically different there will always be multiple distributions with their own needs for package managers.