Firefox was amazing even when Chrome was released
It was just less of everything than Chrome. First install experience for an average user was much better in terms of speed and snappiness. That was one of the keys to its success.
It was good, but slow by comparison at the time.
No need to be revisionist. Chrome brought amazing work to the table. The multiprocess, sandboxed system was incredible - it's not to say that Chrome was the first (IE did it earlier) but it was certainly way ahead of Firefox for a long time. Chrome is the reason we have Seccomp V2 on Linux. Chrome made "software is always up to date" the standard. Before Chrome, Blackhole and PoisonIvy absolutely ruined people's computers - click to play Java, click to play and sandboxed Flash, etc, were massive improvements to every day user security, probably some of the biggest security improvements to computers in my lifetime.
Firefox took a long time to catch up and their CEO was utterly incompetent, which seriously harmed Mozilla.
No it really wasn't. It took Firefox multiple years of catching up, releasing multiprocess architecture, 64-bit binaries (!), ... It took until Firefox 58 (2018) until they finally cought up. There was this huge period of nothingness around 2014 when they focussed on other weird stuff like FirefoxOS that everyone saw from miles away that it will flop.