Linus Torvalds takes most of the cake : Linux + Git. Most developers wouldn't have their job without these two, heck even Github and Gitlab wouldn't exist.
I think that's going a bit far. We'd be using BSD, or a commercial Unix like Solaris. Mercurial, SVN, and god forbid even CVS would still work for most projects.
Seriously, in the dim days of the early 90's it seemed like the overpricing and fragmentation of the various Unix vendors would hand the mid-size and small systems space to NT. Which was all part of Microsoft's plan. The BSDs were themselves too factionalized to be a credible alternative. The Unix wars were winding down and NT was winning.
Linux not only blocked NT's takeover of the data center it also ended the Unix wars and ultimately destroyed the market for incompatible Unixes.