Any purported explanation of Itanium's failure that doesn't even mention compilers once is at best incomplete.
> I won't be surprised at all if the whole multithreading idea turns out to be a
> flop, worse than the "Itanium" approach that was supposed to be so
> terrific - until it turned out that the wished-for compilers were basically
> impossible to write.
>
> - Donald Knuth 4/25/2008 in InformIT [0]
[0] https://www.informit.com/articles/article.aspx?p=1193856