It was eaten by Google flexing their search and mobile monopolies, to advertise it on one of the most visited websites in the world, and coming pre-installed on over a billion devices. Distribution lock in leading to market share dominance is a tale as old as computing to the point that we now have decades old case law specifically on the issue of software monopolies being the cause of browser market share dominance.

Interestingly the most recent anti-trust case against Google, one proposed remedy was spinning off the Chrome browser into its own company, but that option was judged to be unrealistic, because how would a browser survive on it's own without distribution advantages and all its costs subsidized by other revenue drivers? A great question.

There's a lot of opinions and anecdata in that. Firefox was almost never as bad as it was marketed to be (by its competition), and Chrome was certainly never as good as it was marketed to be (by an evil ad company pretending to be a good, well adjusted internet benefit company).