HP saw the disaster coming and designed their own McKinley Itanium, but a bit later, and HP obviously didn't want Dell to have it.
The compiler support was not good outside HP-UX, if I remember correctly.
And then AMD64 happened, and Microsoft told Intel that there would be no further 64-bit PC instruction sets, and the market would choose between AMD and Itanium.
Cue the guillotine.
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"
it sounds interesting