x86-64 did not only kill the Itanium but also all the RISC competitors like Alpha and especially Sparc. While x86 had pretty much pushes the alternatives from the desktop, if you wanted to run a 64 bit server, you had to go with the RISC architectures. When I joined my company in 2005, all the servers were still Sun Sparc and only slowly Opterons got deployed.
Itanium is credited with killing RISC market, IMO much more correctly than attributing it to amd64 - which mopped things up after the great Chipzilla got everyone to cancel before first Itanic started its maiden voyage to the iceberg known as "real world use"
Non trivial amount of know-how and - if rumours to be belied[1] - direct design then went from Alpha team at Compaq to AMD, though Intel retained some of it (AMD already had been doing cooperation with Alpha, leading to the funky case of "jig it enough and an Athlon-MP motherboard might just run an Alpha and Athlon at the same time").
[1] - Once heard from semi-reputable source that an early K8 changelog entry contained "dropping support for VAX floating point formats". Unverifiable unless someone somehow publishes those docs, but it did fit with "That opteron looks suspiciously similar to EV7"
Which is a pity, Solaris SPARC is currently the only server UNIX that makes proper use of hardware memory tagging, while neither AMD nor Intel managed to make a proper implementation of MPX.
