Apple would be doing their own thing anyway. It’s not just about performance, there’s all the myriad other tweaks and customisations you can do on your own SOC to differentiate yourself. We see this with the mobile SOCs. Secure Enclave, sensors, Specialist machine learning accelerators for image processing, exactly the core count and cache you want, optimised bigLittle. The T2 chip is actually a modified iPhone SoC design. With Apple Silicon that can just be a sub-unit in the main SOC.

Yes moving to a new architecture is challenging, but Apple has done it before any this time it can be for keeps. Never again will they be beholden to another company’s priorities, or stuck with me-too processors their competitors have equal access to. A better Intel road map might have resulted in putting the transition off, but I think it was inevitable eventually ever since Apple bought PA Semi.