AMD is getting there by optimizing the shit out of memory access and cache. RISC designs by nature have far simpler memory models. AMD has to throw tons of resources into making the x86 pig stay in the air, and they’re already flirting with a move towards ARM.
Most of the people who know how to keep that pig flying already work at AMD or Intel. They certainly don’t work at VIA Technologies (the third x86 company that nobody talks about, for a good reason). In contrast, any given Fortune 500 could probably hire an ARM team to make a custom chip for their needs provided they had a good enough reason.