Everyone has listed a lot of reasons, and there's also https://manjarno.pages.dev/ which pretty much sums up all the technical reasons.

I'd just like to add why I switched. I used Manjaro for a couple of years, and suggested it to friends and family for a while. It was fine when it worked. But when it didn't, it was a pain to figure out wtf was wrong. Their forum wasn't helpful, and you can't get help in the Arch forums, because it's just different enough. Also, whenever something broke, their logic was always backwards. Like SSL broke for the 5th time, just roll back your clock guys. It felt like being in an abusive relationship with a distro.

I finally switched to EndeavourOS some 4 years ago, and it's been very smooth ever since. In fact, I've had a good experience with pretty much every distro that I've used long term (e.g. AlmaLinux, Debian, Fedora, and even Ubuntu), except for Manjaro.