Every year since 1999 has been declared the year of the Linux desktop. My grandmother still does not use Linux.
My mother asked me to switch her over to Linux about a year ago. Never had an issue since. It wouldn't have been possible without the work wine and steam have done to make playing games on Linux possible.
I've long made using Linux a condition for free IT support. I assist with switching for the willing. It reduces the amount of support I have to do which allows me to support a lot more people. ☺️
It's like smoking, they gotta decide to quit on their own. I had my reasons for staying on Windows for as long as I have.
Server was won pretty quickly as Linux became the only remaining Unix.
Mobile was won because Google picked it as a kernel, however it's at best a pyrrhic victory because the userspace has nothing to do with other Linux.
Desktop also needs a specific event to be won, it won't just grow up progressively for no reason.
To be clear, while Linux has won much of the mobile market - FreeBSD still has roughly a third of the market worldwide, and more than half in the US for an example.