It's worth noting that Chrome was just legitimately a good product in a space where the competition wasn't blowing any minds. The people that switched over saw how much better a browser can be and spread the word.
How the mighty have fallen.
For a couple years Chrome was noticeably faster than IE/FF which is what caused tech oriented people to switch.
FF and even IE closed the gap for a little bit but once Chromes dominance took old I imagine the fact that no one tests things on FF any more has probably caused it to slip performance wise.