I think the idea there is that it's less direct. Intel's lack of interest in a 64-bit x86 spawned AMD x64. The failure of Itanium then let that Linux/AMD x64 kill off the workstation market, and the larger RISC/Unix market. Linux on 32 bit X86 or 64 bit RISC alone was making some headway there, but the Linux/x64 combo is what enabled the full kill off.
Intel's lack of interest in delivering 64bit for "peons" running x86 also was part - I remember when first discussion in popular computer magazines showed of amd64, that intel's proposed timeline was discussed, and it very much indicated a wish to push for "buy our super expensive stuff" and trying to squeeze money.
Meanwhile the decision to keep Itanium on expensive but lower-volume market meant that there simply wasn't much market growth, especially once non-technical part of killing other RISCs failed. Ultimately Itanium was left as recommended way in some markets to run Oracle databases (due to partnership between Oracle and HP) and not much else, while shops that used other RISC platforms either migrated to AMD64, or moved to other RISC platforms (even forcing HP to resurrect Alpha for last one gen)
