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.
http://en.wikipedia.org/wiki/WinG
Gabe Newell had nothing to do with it.
OMG, the comments below that first post are full of ignorance. It's just so painful to see what people think and say of Linux (even the ones who defend it).
That's a bit simplified. More details about this story can be found in the very entertaining book "Masters of Doom" (about John Carmack and John Romero).
I would think that times were a bit different back then, and it's not really a fair comparison to make.
Companies today that are the size of id software back then, and that are making games of relatively equal complexity, are already publishing to Linux.
There were no 200-person studios cranking out $10 million dollar (or more) game projects when Doom came out, and that's a much more complex issue to address..
We're barely seeing OS X ports of major titles now, so while I think SteamOS is great, I don't think it's going to suddenly mean an influx of AAA Windows titles appearing on Linux.
Although DOOM95 was not a success, it doesn't mean that what Newell believe was wrong. Also it's pretty clear that many people buy/use computer for solely entertainment purpose and that's why consoles sold.
WAIT. Newell's Windows port (commonly referred to as DOOM95 http://doom.wikia.com/wiki/Doom95) was never popular and very few DOOM players knew it even existed. It certainly didn't prove to the masses that Windows was a viable gaming platform.
Those that do recall the Windows port do so in the the context of Microsoft telling people that '32 bit Doom will be twice as fast' before finding out that wasn't true.
The most popular - read 'only' - PC version of Doom was the DOS 4GW version. Ditto Doom 2, Hexen, etc. Quake also assumed DOS. No Windows port of those games was mainstream. Go read the DOOM FAQ - everything assumes DOS, DOOM95/WinDOOM is only mentioned as one of many ports of 'regular' (DOS) DOOM http://www.gamers.org/docs/FAQ/doomfaq/sect1.html#5-6).
DOOM was released in the era of 386s (when 486s were new). 32 bit Windows required at practically at least 16MB of memory and a 486. For the people that had those specs, if the Windows DOOM port was faster, people would have used it - but they didn't, because DOOM95 wasn't faster.
DOOM95 may have been used to inspire developers however - the regular PC version of Quake 2 came with a Windows installer / launcher and was frequently launched on Windows.
Source: spent my teenage years building stuff like http://mikemaccana.com/#/doom-the-path/ in DEU, the first algorithm I ever heard of was BSP, and I know what IDSPISPOPD stands for.
PS. Go play my and John's WAD linked above. It has working toilets. In DOOM!