Rather, Microsoft is (or was, in the pre-post-PC world) everywhere because of (a) licensing stitch-ups with hardware vendors and (b) network externalities: get into Corporate IT departments with Office, then people will want (or need) to use the same OS at home, and then you can strong-arm hardware vendors into signing exclusive Windows-only-on-our-PCs licensing deals, which in turn convinces Corporate IT that there's no viable alternative to a Windows-only ecosystem ...
Arguments about whether or not Linux is fit for desktop use by non-technical users miss the point: Windows' monopoly status was a virtuous circle (for a value of "virtuous" that approximates to "in the interests of MSFTs shareholders and provides job security for MCSEs") until the wheels fell off when confronted with an even bigger ecosystem that came out of nowhere. Which is the magic rabbit Apple pulled out of a hat with the iPad, and Google seeks to emulate with Android.
The desktop is now irrelevant -- less than 10% of computing devices people use are desktops or laptops: it's all gone mobile frighteningly fast -- but for what it's worth, Linux won. Because the winning Linux desktop is actually a phonetop or tablet environment: Android.