Itanium was a really bad architecture for the time (and possibly still is). It was a bet that sufficiently smart compilers would be available, but they weren’t

Itanium was a really bad architecture for the time (and possibly still is). It was a bet that sufficiently smart compilers would be available, but they weren’t available in time. They aren’t even available today 20 years down the line in a form that would have justified Itanium if they were available then. It wouldn’t have mattered if Intel controlled the OS or not - it just wasn’t competitive. There’s nothing you can learn from it about Apple - who delivered an ultra competitive, likely even when emulating Intel architecture in software.