There was less software running on PowerPC than x86 back then and still there's less software running on Arm than x86, especially the key ones like professional ones (above all, Adobe suite, AutoCAD, Blender, Ableton, etc.)
Arm chips might even be faster for Apple, but MacOS X unfortunately isn't as castrated as iOS and power users will refuse to give away that (small) liberty available in the desktop system than on mobile one.
An OS where there's only a way to install software (the AppStore) is a huge limitation and even Microsoft itself learned the mistake with Windows 10 S, offering customers to install the standard version.
Apple has already done this a few times before. I'm sure internally they've decided whether they need buy-in from a critical-mass of apps like Word and Photoshop (or maybe they feel they don't anymore). I'm pretty sure the Carbon API was a concession made because Adobe wasn't going to port Photoshop (they still took 10 years to do it). Apple will reach out to those companies individually and coordinate something if they feel it's needed. They often demo these things live at the announcements.
At least this time Adobe has already ported the "core" of Photoshop for iPad Pros last year. Microsoft had Word running on Windows 10 on Arm (I think they merged the mac/windows codebases a bunch of years ago?)
I think the biggest question is what will happen with OpenGL because so far I don't see pro apps adopting Metal.
I have also seen the point made that many/most modern desktop apps are just Electron apps: not too many people/companies are invested in Cocoa these days. Adobe/Microsoft are the big obvious exceptions. Computers are fast enough to enable what might otherwise be called "bloat."
Arm chips might even be faster for Apple, but MacOS X unfortunately isn't as castrated as iOS and power users will refuse to give away that (small) liberty available in the desktop system than on mobile one.
An OS where there's only a way to install software (the AppStore) is a huge limitation and even Microsoft itself learned the mistake with Windows 10 S, offering customers to install the standard version.