Joe Wilcox over at Microsoft Watch today wrote a piece entitled "Operating Systems Don't Matter".
That, in my humble opinion, made all the difference. Digital Research never went public and by 1991 had been bought by Novell and eventually faded into computing history. Microsoft went public, kept buidling applications and, to my continuing bemusement, I now work there (not building applications mind you but creating tools for those that do).
I have to disagree, to a point. The OS that does the best job supporting developers that make the applications matter. One thing Microsoft has done well is to
suck up to cultivate relations with developers. Microsoft has tried to provide a way for not only professionals, but the casual developer as well to program. Even now you can get free versions of Visual Studio. Linux is free as well, but Visual Studio has more, or at least more civilized, support for the novice. Some of the Linux crusties can be brutal when presented with 'stupid questions.'
If another OS was to make programming easier, or offer more to the developer, they would switch OS's in a heartbeat.