To be fair, running on anything in the top 500 is a pain in the butt. Cray's are a major pain. I hear the NSCCs computers (TaihuLight and Tianhe) are essentially linpack machines, in reference to their difficulty. But I've never used them. HPC is just overall difficult and frustrating. But it is getting better.
But if we look at servers, there's a ton of Linux servers out there. Might be a better metric than computers that a small subset of programmers use. Linux accounts for >30% of this share and Unix like is >60%. Those are really important.
Also a lot of embedded systems run Linux.
Either way I think we pretty much agree. Linux is everywhere. Just not big on desktops. But huge everywhere else (which has a larger share of the computing resources in the world).
Or servers, or mobile devices in the form of Android phones. Desktop usage is only one many use cases for Linux.