Okay? Red Hat Enterprise Linux wasn't released until 2000, so I don't know what Microsoft's late-80s UNIX distribution has to do with it. Google was running Linux from the early days, and they launched in 1998, which is nearly a decade after Xenix stopped being updated.
EDIT: Yes, Linux has its origins sooner, and if you want to know why Linux beat the BSDs to mindshare, what was going on in 1993 is very important. But Linux wasn't competing for mindshare with Xenix, it was stuff like Solaris (which did have an x86 port, but was mostly running on SPARC), AIX (which was mostly IBM big-iron and POWER), HP-UX (which was PA-RISC and IA-64), etc.
If you want to talk about post-1993, saying that Linux won because there weren't any commercial x86 Unices makes even less sense. Xenix did not stop being updated, it became SCO UNIX. SCO bought and continued to sell UnixWare from Novell in 1995. x86 Solaris came out in 1993, but Sun actually had an x86 Unix since 1991 when they bought ISC.
EDIT: Yes, Linux has its origins sooner, and if you want to know why Linux beat the BSDs to mindshare, what was going on in 1993 is very important. But Linux wasn't competing for mindshare with Xenix, it was stuff like Solaris (which did have an x86 port, but was mostly running on SPARC), AIX (which was mostly IBM big-iron and POWER), HP-UX (which was PA-RISC and IA-64), etc.