Windows (for many years) -> Ubuntu (for a year) -> Arch Linux (for half a year) -> Void Linux (literally 2 days) -> Artix Linux with runit (a month) -> Gentoo Linux (another month) -> Debian (finally, I don't plan on changing it).
In the 90's: Slackware, then RedHat, then Debian, then Progeny (Debian based), then shortly Mandrake (RedHat based)
Early 2000's: RedHat Japanese edition, TurboLinux (because I was in Japan and Japanese IME was almost impossible to get working on non-Japanese distributions)
Then I had fun with Gentoo looking at my terminal compiling stuff everyday and fixing broken package because I followed advices to activate crazy compilation flags
Nothing in particular, for the past few years I didn't like the direction Ubuntu was taking but I stayed because I was too lazy to switch and it didn't feel that bad.
So I'm not sure exactly what was the last straw, maybe part of it was me getting a Steam Deck, discovering flatpak and understanding how bad snap was compared to it.
It just works, just like Ubuntu before they started pushing snap down everyone's throat (which is what made me switch eventually.)
I had a bad image of RedHat/Fedora's package management from the time deb was much superior, but no they caught up and are on the same level (I know, it's probably been a while).
I also like how they mostly package upstream without too many changes. When Ubuntu started upstream was a bit lacking so making changes was necessary to get something that looks like a consistent OS rather than a patchwork of packages, but now it's no longer needed. Ubuntu is no longer the only distribution with that level of polish.