Chrome is, and majorly was, pushed by Google websites. Using one near monopoly to create another.
Also, Firefox never defeated Internet Explorer. You are misremembering that. Firefox once made impressive market gains despite the anticompetitive competitor bundling. That doesn't mean it's feasible to keep doing it.
IE also never had mountains of supposedly techy people instructing naive users to use Chrome because "it's faster", which was only true in the very beginning, as if saving 200ms per page load is worth putting Google in full control of the internet.
Er, Mozilla marketshare on Android is low because of Google anti competitively bundling Chrome with the Play Store.