HP, DEC/Compaq, and SGI all made the decision to drop their various bespoke architectures for Itanium years before prototypes were available based solely on what Intel claimed performance would be on paper. Even Sun and IBM made noise about doing the same thing. Honestly, I think it was inevitable that something like this would happen. By the late 90s, it was starting to get too expensive for each individual high-end server/workstation company to continue investing in high-performance chip design and leading edge fabs to make low-volume parts, so it made sense for all of them to standardize on a common architecture. The mistake everyone made was choosing Itanium to be the industry standard.