After Stallman launched the GNU project, the emergence of GNU licensed kernel for x86 architecture was inevitable. It just happened that Linux became that kernel. Had it not, the GNU project folks led by rms would have inevitably made their own.

I'm not sure this is guaranteed. GNU and the FSF have absolutely provided an enormous amount to the concepts and implementation of OS software. No doubt about it. Without it Linux would not exist, but it doesn't mean that'd have resulted in a widely used GNU alternative.

BUT, GNU/FSF also has a long history of losing focus on coding and spending a lot of time on political and philosophical arguments. I think it more likely BSD may have headed to where linux ended up than GNU. Linux was successful because they moved forwards and arguments were settled relatively quickly (for better and worse), whereas Hurd got stuck in development hell as people argued over how pure the microkernel architecture should be, pushing away people who just wanted things to work - including volunteers. During the crucial period over the 1990s, open source software needed to get things done (kind of like a startup). There are videos out there of people speaking at conferences about their work on Linux, and RMS being in the audience interjecting that it's "GNU/Linux" every time Linux was uttered. Who wants to work in an environment like that?

Even today, people are looking at more and more alternatives to important GNU software because of stagnation or other technical merits. GCC has lately seen alternatives become more common, as an example.

This also ignores the hostility the FSF historically has/had towards the commercial industry. Torvalds largely accepted patches from anybody if the code worked as intended.

Maybe something could have come out, but my gut tells me that people would have gravitated to something else that worked.