We're talking about two different things. OP was not talking about ARM ISA, but Apple silicon. Mobile switched to Apple silicon under Jobs with iPhone 4 https://en.wikipedia.org/wiki/Apple_silicon. Apple designed cores were added later, also under Jobs. Apple silicon, Apple cores => Jobs.
Moving laptops to ARM ISA with Apple cores can be credited to Cook, but it was not a big move or a risky step like standing up their own CPU design team was. From the release of Swift and onwards, all the punters were speculating about when (not if) it would happen, and you could really plot a performance line for Apple vs Intel/AMD CPUs and make a pretty educated guess when it would happen.
And yes, the powerpc and x86 switches gave them a lot of experience doing the ARM switch, with fast emulation, fat binaries, etc., and others like IBM had implemented TSO modes in weakly ordered CPUs and others like Transmeta had special instructions for x86 flags emulation. It wasn't really a huge technical gamble beyond what Cook inherited to move to ARM.
Moving laptops to ARM ISA with Apple cores can be credited to Cook, but it was not a big move or a risky step like standing up their own CPU design team was. From the release of Swift and onwards, all the punters were speculating about when (not if) it would happen, and you could really plot a performance line for Apple vs Intel/AMD CPUs and make a pretty educated guess when it would happen.
And yes, the powerpc and x86 switches gave them a lot of experience doing the ARM switch, with fast emulation, fat binaries, etc., and others like IBM had implemented TSO modes in weakly ordered CPUs and others like Transmeta had special instructions for x86 flags emulation. It wasn't really a huge technical gamble beyond what Cook inherited to move to ARM.