You’re kidding me. Are you seriously happy with the level of innovation coming out of x86? It’s a decades old pile of glue and skeletons. Intel has all but given up. AMD is out innovating Intel but at the end of the day the platform as a whole is aging and comes with a lot of baggage, spectre/meltdown, etc...
You can certainly choose to view this as a step towards bolstering the walled garden... but my money is on Apple wanting to innovate and knowing that they can. Vertical integration does a lot for efficiency, cost, etc... as well and not just keeping people in your walled garden.
People forget: Apple has been shipping their own silicon for years. If you had stellar cpus you could make in house, wouldn’t you rather use them instead?