Curiosity. Then starting development and figuring out most things non-MS specific assume UNIX/Linux based. I'm not obsessed at all, I quite enjoy macOS, and don't mind Windows too much for what I do with it, but it's my OS of choice for development machines, and any servers I control.
Same here. Curiosity which changed in time to my work.
I even was using win10 + wsl in company, but after time of adding crapware + forced win11 update (downgrade) I just said "gimme Linux laptop". Gave up totally, useless for me
On personal hardware - Linux is first choice, omly gaming pc is Windows based.