Linux is super fragmented (and generally has been historically).
If more people in Linux agreed to develop, use, and support the same distro–similarly to how most of us use the same kernel–then that distro would probably be better than Windows and more people would move to Linux.
It’s kind of happening naturally as it picks up more users and developers. There are really only a few distros that all others are based on. And as many have already said, it’s not fragmented and actually very healthy, and that’s a good thing.