I mean if it's just about performance, why switch architectures instead of using AMD chips?
Apple: People who are really serious about hardware make their own processors.
So you don't have to kill all of the software currently running on your customers' machines.
I bought a PPC Mac 9 months after they first made the switch. Most of my software was already native. Within the next year, all of the important software was native.
With recent changes to the OS, a decade of instability with every update every year, the recent hard deprecation of 32 bit binaries, and now moving to an unproven ISA for those particular workloads - all while Windows and Linux have closed the gap, mostly... the situation is a bit different.