Designing their own chips in-house wasn't "their expertise" either, a few years ago. You won't expand into other areas unless you at least make it a priority and try.
Getting into semiconductors is probably substantially more complicated. Only a handful of companies are able to do it well and they have bene at it for decades.
I think a few years ago there were rumblings about a 2/3nm Apple fab being made in Berlin, but I've heard nothing about it since, so it may be a lie.
That being said; the other commenter is right. If Apple had to release the M1 on 10nm or even 7nm, they would end up sacrificing at least >200% performance-per-watt; a death blow to either the battery life or performance. Apple's move to dominate the 5nm supply was another demonstration of their manipulation of supply chains akin to their iPod hard drives. There are indeed interesting parts of Apple Silicon, but the performance is driven wholly by their exclusive 5nm ARM cores.
It is getting tiring to hear the same lies over and over again on this site. Extraordinary claims need extraordinary evidence. Show me a clear proof that Apple's performance per watt is reliant to a 200% improvement on the 5nm process. Perhaps I can point you in the direction of the A13 (https://en.wikipedia.org/wiki/Apple_A13), Apple's last 7nm chip. Apple claims their subsequent 5nm node (A14) is 40% more performant than that one.
7nm is considerably less dense than 5nm, since it's increased size compounds across two dimensions. That being said, A13 was indeed on 7nm, as well as the A14x they put in the dev kit. I don't think those benchmark numbers would be competitive against 3D Cache Ryzen or current Alder Lake offerings. Furthermore, I question how far Apple will be able to push Apple Silicon. As we've seen with the M2, when Apple can't get a clean node upgrade, they're forced to increase heat/power like Intel and AMD so they can scale their performance. With the upgrade to 3nm being much less dramatic than 10nm -> 5nm (and with Intel catching up rapidly), Apple is under extreme pressure to engineer themselves out of this situation. It may not be technically feasible.
So, let's do some quick math. Assuming the A12z runs in the same power envelope as the M1, it uses roughly half the power of the preceding Intel chip. That makes sense, since both the performance and efficiency cores are using a much denser process. Generously speaking, both of these chips have a similar performance profile, which leads me to believe that Apple's real 'boon' here was simply switching to a denser node. Comparing IPC across ISAs is largely guesswork, but I'm not convinced that AMD or Intel are incapable of manufacturing 5nm chips that decimate Apple's offerings. Apple hasn't allowed it to happen, so we can't say for sure.
Are you comparing an x64 chip with an ARM one and then deciding the only difference is the node process?
We’re talking here about what is unequivocally the most complex manufactured goods in the world. You can’t just boil it down to one thing. Apple made so many decisions that lead them to their extraordinary performance, including financial ones. They heavily paid TSMC for priority access to their new node.
And once again, the gains are nowhere near 200%, your initial claim that is patently wrong and that you refuse to acknowledge as a mistake on your part.