Itanium was essentially (incompatible) PA-RISC 3 - it originated as HP project and the direction to totally replace HPPA with Itanium was there from the start.

Non-Stop got ported early on because they needed some hardware and clients were locked down.

OpenVMS customers however balked about shifting to Itanium given that it was often slower than their existing Alpha boxes, leading to HP being forced to finish EV7 work and release another generation of Alpha chips (funnily enough, EV7 might have forked and lived on in Opteron/K8...)