The driver instability was only their fault. The fact is the reason AMD64 "won" was because in the late 2004 era, with SP2, Microsoft killed PAE (the concept, not the implementation, by artificially limiting addressable memory), and the artificial memory limit on 32 bit systems doomed the architecture.
I speak only of the time period from 2004 - 2008 where we went from Pentium 4 to Core 2 (and Athlon64 to Phenom), where 64 bit became ubiquitous because Microsoft failed to provide its consumer grade OSes the ability to access the amounts of memory the hardware supported.
