Itanium only failed because AMD was allowed to come up with AMD64, Intel would have managed to push Itanium no matter what, if there were no alternatives to a 64bit compatible x86 CPU.
Itanium wasn't x86 compatible, it used the EPIC VLIW instruction set. It relied heavily on compiler optimization that never really materialized. I think it was called speculative precompilation or something like that. The Itanium suffered in two ways that had interplay with one another. The first is that it was very latency sensitive and non-deterministic fetches stalled it. The second was there often weren't enough parallel instructions to execute simultaneously. In both cases the processor spent a lot of time executing NOPs.
Modern CPUs have moved towards becoming simpler and more flexible in their execution with specialized hardware (GPUs, etc) for the more parallel and repetitive tasks that Itanium excelled at.
I doubt that Itanium would have ever perked down to consumer level devices. It was ill suited for that workload because it was designed for highly parallel work loads. It was still struggling with server workloads at the time it was discontinued.
At Itanium's launch, an x86 Windows Server could use Physical Address Extension to support 128GBs of RAM. In an alt timeline where x86-64 never happened, we'd have likely seen PAE perk down to consumer level operating systems to support greater than 4GB of RAM. It was supported on all popular consumer x86 CPUs from Intel and AMD at the time.
The primary reasons we have the technologies we have today was wide availability and wide support. Itanium never achieved either. In a timeline without x86-64 there might have been room for IBM Power to compete with Xeon/Opteron/Itanium. The console wars would have still developed the underlying technologies used by Nvidia for it's ML products, and Intel would likely be devoting resource into making Itanium an ML powerhouse.
We'd be stuck with x86, ARM or Power as a desktop option.
