Firefox succeeded because the only other option at the time was IE6 and Firefox was far superior to IE6, especially among developers. It was Firefox that first gave us developer tools. Do you remember web development in the days before developer tools?
The web also nurtured the GNU/Linux server. Apache on Linux slaughtered IIS on Windows and itself got killed by Nginx on Linux in turn. The web giveth, the web taketh away...
The majority of web stacks, regardless of language, run on Linux.
ISP providers choose GNU/Linux because one cannot argue against free (gratis) that works good enough.
All the programming languages I care and use for web applications have zero dependencies on OS specific APIs, some of which I can even run bare metal or on an unikernel, with zero code changes.
The cloud concept, Web APIs and serverless executions, the OS of server running my web application is irrelevant, thanks to rich runtimes.
As for Apache and IIS, they are pretty much alive outside HN bubble.
The web, specifically Electron, is why I can run a bunch of modern applications on my Linux desktop and I don't have to switch to another OS to use eg. Discord.
