Well, those of us that were already coding for Windows back then, remember that what brought game studios to Windows was WinG, the percursor of DirectX.
Came here to say this. Gabe is welcome to his version of events but like all humans is suffering from selective memory syndrome. Alex St. John is the one who "made it happen" in my recollection, and I was pretty close to the action.
Yeah, Gabe's role is massively overstated here, but it's important to remember how awful a development platform Windows was for games, that compared to DOS it was far, far worse than Linux is today.
In DOS mode you could easily get full-screen, high-frame rate game graphics. In Windows you'd be lucky if you could push more than one frame per second, the Windows GDI was absolutely brutal.
Linux is a lot further ahead, so SteamOS has a relative head start. If Windows can be made into a first-class gaming platform, so can Linux.
I completely forgot about WinG. I think I remember a test it ran when installing to find the fastest way to blit bitmaps. A tiled curvy red line that would flip tile directions back and forth.
Gabe Newell worked for Microsoft at the time in question. He is saying that as a principal Microsoft employee he initiated the port of Doom because Microsoft saw the problem getting game authors to target Windows. Notable that Alex St. John then led the development team, for those who note his obvious importance in gaming on Windows.