The ia64 more complex compiler ecosystem made it difficult or impossible to port performant programs to the platform. Amd64 allowed people to keep building and running most programs with little understanding of what was happening in the architectural layers.

Even the 800lb guerilla Intel had to acknowledge amd64 was the next step, or it could end up a niche use chip like PowerPC.

The moral of the story is usability matters with consumer chip architecture. =3