Just because Itanium last as a bet, doesn't mean it was wrong to try it. They gambled that compilers would keep up - they didn't. Today it might work! Compiler technology is very much improved. (Dotnet/Java payloads? Dynamic recompiling...) It's a software problem and as such inherently easy to underestimate the complexity of it. Itanium also had its roots in a time when Big Iron was more relevant than it is today.