What is so "obvious" about it?

The fact that Apple develops and ships hundreds of millions of ARM processors every year, which are widely regarded to be the best ARM processors made, and they design and ship no X86 processors?

That alone doesn't make it "obvious" as applied _to a Mac_, which is a very different kind of device that caters to a different audience that often has special needs. See our other discussion threads elsewhere.

That is what I explain in the link. I saw this move coming two years ago when I wrote that article. I noticed how regular users were using iPhones and iPads for almost everything they do. I noticed how office apps like Pages, Keynote and Numbers worked without any performance issues on iPad.

I concluded ARM was fast enough for 90% of users. Once you don't have the restriction of battery life and small enclosure it is not hard to imagine that Apple could beef up ARM a lot for their desktops and laptops.

Why run multiple CPU architectures when one does the job and is much cheaper?

I've been thinking hard about what kind of workload ARM can't handle and I can't think of anything. Ok... there is one 1st person shooter games. But iOS is a more successful gaming platform than Mac.

Macs have at least two major uses that might present technical problems: native MS office apps, and VMs for developers.