Firefox was significantly better than IE though: it was faster, had more features, and things like that. This is what made Firefox popular, not "sheer force of nerds".
Chrome, when released, also had some significant improvements to Firefox. In particular, it was loads faster. This changed with "Firefox Quantum" (59 IIRC), but "too little, too late" I guess.
Alternatives need to be built and advertised.
Firefox was better because it had tabbed browsing, integrated search, pop-up blocking, and extensions, but I was responsible for monitoring our perf back then and I can say for certain that we were not faster.