The premise here is wrong. arm64 is the Apple ISA, it was designed to enable Apple’s microarchitecture plans. There’s a reason Apple’s first 64 bit core (Cyclone) was years ahead of everyone else, and it isn’t just caches. https://twitter.com/TheKanter/status/1345951964484390912
Arm64 didn’t appear out of nowhere, Apple contracted ARM to design a new ISA for its purposes. When Apple began selling iPhones containing arm64 chips, ARM hadn’t even finished their own core design to license to others.
ARM designed a standard that serves its clients and gets feedback from them on ISA evolution. In 2010 few cared about a 64-bit ARM core. Samsung & Qualcomm, the biggest mobile vendors, were certainly caught unaware by it when Apple shipped in 2013.
Apple planned to go super-wide with low clocks, highly OoO, highly speculative. They needed an ISA to enable that, which ARM provided.

M1 performance is not so because of the ARM ISA, the ARM ISA is so because of Apple core performance plans a decade ago.
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