> beat MS's proverbial posterior because the browser was better
not via marketshare. The fact is, only developers (and adjacent) were using firefox. IE, during those days (pre-chrome) was still such a dominant browser that you had to check for IE compatibility.
But today, developers are not checking for firefox compatibility. So, firefox today (and during the firefox heyday) were never truly "beating" IE from a marketshare perspective.
I remember friends of same age to also actually switch browsers by themselves, suddenly finding that their computer now used Firefox instead because it was simply faster. Same reason everyone switched to Chrome at a later point.
not via marketshare
That's not an entirely fair measure though, considering Microsoft lost an antitrust case that was brought because they were unfairly leveraging their monopoly in operating systems to give them an advantage in browser adoption. The DOJ threatened to break up Microsoft over it, and eventually only stopped when Microsoft added an option for users to pick a difference default browser over IE.
By that time IE's dominance was beyond Mozilla's reach and it was only when Google leveraged their monopoly in online advertising that a real alternative option for users became viable.
https://en.wikipedia.org/wiki/United_States_v._Microsoft_Cor....
There was a period of time when our university help desk was installing and recommending Firefox for students and faculty to use over ie6.