Yeah, it’s technically complicated. The “5” in RISC V kinda denotes the history involved in this (IIRC). I’ve seen a bunch of stuff on this, but it has been awhile and my attempt to focus may misconstrue the blur in my mind. So don’t take this as gospel. The previous attempts at a completely open ISA were failures in that they weren’t compatible with the foundry toolchains or peripheral business licenses and tech. They tried to do too much or force change tenured elements that have no open source replacement. RISC V was the first to be practical and garner support from industry and academia. There was a major hurtle that it had to overcome early on. As soon as this happened, the sale of ARM was announced shortly thereafter. I forget the details. It was in a conference talk on YT IIRC. I just recall thinking, that the timing of the sale of ARM spoke volumes about what RISC V is in the grand scheme of things. In 10 years time, I think everything will be RISC V. It will dominate in every sector from small microcontrollers all the way to the largest data centers and everything in between. It will be the final blow to x86, ARM, and anyone that fails to migrate quickly. This is Linux for hardware and fixes a lot of problems that are unaddressed with this proprietary crap designed in closed rooms by a few hundred people. No company or group is smarter than the whole world with unrestricted access.
The one thing Apple has always been really good at is picking dying architecture for their hardware. If Apple uses it, the hardware is practically doomed. (6502/68k/power PC/ARM)