It's the OS. The application distribution model is, in my opinion, significantly better than Linux and it's package management/repo scheme. I don't have to recompile old software to keep using it 2 years later (or 10 for that matter), I can place applications on different disks than the OS resides on, I can keep multiple versions of the same application, etc.

Is there a difference really? Microsoft spent years and literally billions to get developers on their OS (see Balmer's "developers developers developers" speech in the nineties). Of course some people consider this evil.

No and no. Windows is "the better fit" because: 1) AD. 2) corruption (it's a very long story, see Munich for one). 3) anticompetitive behavior. 4) Excel.