Intel & AMD have a cross-license agreement covering everything x86 (and x86_64) thanks to lots and lots of lawsuits over their many years of competition.

So while Intel had to bow to AMD's success and give up Itanium, they weren't then limited by that and could proceed to iterate on top of it.

Meanwhile it'll be a cold day in hell before Nvidia licenses anything about CUDA to AMD, much less allows AMD to iterate on top of it.