By making it free, equally stable, and updated to deal with modern hardware and security issues? By making it ubiquitous enough to have a wealth of software available for it and a ton of resources, including documentation, for it? By making it available to the mass of people who are interested in editing, improving, and supporting it? By being large enough to get OEMs interested in supporting it with things like drivers and other compatibility issues? You know, to name a few reasons. ;-) Keep in mind that I'm an old Unix user - from many years ago. I do love me some Unix, and spent years working pretty closely with DEC and, eventually, Sun - as in a partner relationship 'cause we had some pretty intensive computation needs. So, I do love me some Unix - but Linux is (today) a better choice. The BSD family is also a good choice - but they're just Unix-like and aren't actually Unix. MacOS is also Unix-like, but not *really* Unix. Most Unixes are pretty much dead and are being used in a very limited space. Most of that workload has long since been taken over by Linux. To try to put this into perspective... In every possible way (except aesthetics) a 2018 Honda Accord is better than a 1960 Chevy Corvette. By every possible *objective* metric - every last one, including performance metrics, the Accord is a better car. Subjectively, we may prefer the old Corvette. Subjectively, it may look better. However, the modern Accord has a better 0 to 60, lateral acceleration, efficiency, reliability, safety, carries more, has more features, is more comfortable, handles better, etc... Today, Unix is the old Corvette. Linux is the modern Honda Accord.