that's why microsoft needs to be scared
Microsoft will be scared once Linux can perfectly run just about any Win32 software without a hitch since
it's the most stable ABI there is. Steam Machine and Steam Deck will only make a small dent in their desktop dominance. Some people will be happy with how the Machine/Deck is set up, some will try and move to Linux on their desktops, but the majority will still be on Windows, as most other software that people use still only runs on there. Adobe, Autodesk, MS Office, and dozens upon dozens of lesser programs used in businesses and workspaces that run on Windows, demanding Windows use. That's Microsoft's biggest stronghold right now, and once Linux start eating into that, then the fear will start.
However, any and all pushes in FOSS that lead to better alternatives all stem from other businesses being too fed up with the company behind a product, pushing for a open solution as that's just easier and more beneficial to all corpos in the end. The Linux kernel is the powerhouse it is today only because big corpos saw a massive benefit in being able to all work on a Unix clone without having to go through back-and-forths with Sun/HP/IBM/whatever and, again, being beholden to some corpo for their own business to run. Without that (and without GNU GPL v2), Linux would forever remain this hobbyist OS of some student in Helsinki.
Similarly, the reason Blender became such a magnificent piece of software is because everyone was sick of Autodesk and 3DS Max being a steaming pile of shit. That's when a massive development push happened when we got Blender 2.8 and all the subsequent versions where Blender is now the industry standard and it's completely free. Or OBS, where the biggest sponsors are the streaming platforms and GPU manufacturers. The wide availability of solid streaming software is at a net benefit to them, and it's much better to have it open than to be beholden to companies like SplitmediaLabs. But those are far and few in-between. For example we still don't have an equivalent competitor for the Adobe suite or Autodesk's CAD software that's still the industry standard.
Microsoft's biggest worry right now is making sure that they won't enshittify 11 with broken monthly updates to the point where it can't even do it's basic job of being a Windows NT OS and running Win32 software. Valve's efforts are largely overestimated in the ultimate OS market share as that's all just games, and what Valve is doing isn't aiming to dethrone Windows on their Steam Survey stats, but to have an avenue to offer Steam games that isn't dependent on Microsoft. Going back to the Steam Survey stats, if you were to look at the yearly growth of the Linux users, but account for Steam Deck users, the uptick would be much smaller. And you can't really account for whether or not someone ditched Windows for Linux so those stats aren't a good representation of Linux eating into Windows' market share to begin with, since you'll want for existing users to switch over, not just for new users to start off on Linux.
Then again, like I said, Linux is faaaar from being a serious threat to Windows. Once Wine developers collectively pull their heads out of their own asses and get some proper backing to make Win32 the ultimate ABI on Linux,
then we can talk about Linux dominance.