Yeah, I wasn't trying to say even in the next 20 years you'll see it topple, Windows will be around for a long while. That being said look at the adoption of Win 11 vs 10 and 7, especially in underserved area's of the world that can't afford the next new thing. 10 and 7 still have a healthy foot hold. In the future I can see those communities swapping to Linux to make their older hardware play nicer for their purposes.
Also the reason Linux is so shattered IS because as you said 1) hardware min/maxxing sometimes requires it and 2) They can, it's open source so it's a possibility that can't be done with Windows
Android has similar issues and it's the leader in the mobile market so it's not impossible for it to happen. Just no one cares enough to really make a go for it. Valve's the biggest name in a while to even both TRYING to touch consumer markets on the Linux platform on PCs and as you said, even that is mostly because they were making an OS for their dedicated device, just seems to have steam rolled (pun fully intended) into something bigger than I think even they were initially thinking it would.
I think a lot of it is the Linux community is just happy to see their hobby/opinions being highlighted more often again. Linux for a long while was relegated to server admins, "hackers", and hobbyists (and mostly as you said still is). The attention towards something they enjoy is always a palpable excitement, it just sometimes gets carried away with all the "We're doing it boys! Windows is going down!". Like listening to Cleveland Browns fans talk about going to the Super Bowl, it just isn't going to happen... lol