Might be a case of sunk cost fallacy. The article mentions that while vendors were asking for 64 bit, they didn't want to cannibalize Itanium, but were forced

Might be a case of sunk cost fallacy. The article mentions that while vendors were asking for 64 bit, they didn't want to cannibalize Itanium, but were forced to anyway when AMD came out with their 64 bit pentium compatible CPU.