I only know about the transition to x86 and from what I remember the benefit was the same architecture as Windows. Since them OSX has gained a lot of market share. Moving to ARM is definitely a step backwards in that regard. I don't know anything about the previous transitions.
I don't think transitioning to ARM is a bad choice given the benefits, but a lot of serious (and casual) users are going to be very unhappy their programs aren't going to work after dropping $1k+ on a new computer.
The Mac was already on an upward trajectory before the x86 transition. OS X hasn’t really gained that much marketshare. Besides the “beleaguered years”, Macs have historically trended at around 10% market share. They actually had more marketshare in the early 90s before Windows 95.
Apple has done this three times if you include the Apple //e transition. Each time they brought customer’s along.
The first transition from 68K to PPC, almost all of their revenue came from Macs. The second time about half (the other half was iPods). Now it’s less than 10%. It’s much less risky this time.
I don't think transitioning to ARM is a bad choice given the benefits, but a lot of serious (and casual) users are going to be very unhappy their programs aren't going to work after dropping $1k+ on a new computer.