Fun read.
My short version if I were to write this article would have been:
Microsoft killed it by including Internet Explorer for free with Windows. As IE got better and better less people bothered switching to Netscape which fell further and further behind due to a dwindling user base. It's hard to compete with subsidized 'free',
It spun off into Phoenix (later renamed to Firefox) whilst AOL took over the mainline just to let it die.
Firefox later took over massive amounts of market share from age-old rival Internet Explorer by offering tabs and extension support.
and if you want to continue to the current time line:
Due to Firefox gaining marketshare Microsoft finally started working on Internet Explorer again, it it been neglected for years at the point, this gained then back a few percentages. However it's Google with Chrome that seems to have the last laugh as they marketed on being a faster browser and pushed it heavily on their own platforms that almost every internet user visits daily. Although Firefox nowadays is also very performant its small market share will make it hard to keep up with Chrome.
It might also be worth to mention that the perceived speed advantage might not have been as relevant as it actually was as Google on YouTube for example used a
deprecated API that performed 5 times worse on Firefox then it did on Chrome.
--
This is from someone who has used Phoenix and Firefox since day 1 and still uses it. In my personal opinion (as a web developer) Google using a deprecated API for YouTube was purely to push people onto Chrome.
Step 1 of enshittification

Step 2: Make adblockers worse by forcing developers onto Manifest v3.
Step 3: ??? My guess is: Make adblockers even worse or ban them entirely like they're trying on YouTube at the moment.
My advice: Use FireFox, it has a long history of putting users first unlike Google. Non-profits are easier to trust than for profits.