Apple Silicon
was autopilot. Or more specifically the insanely cool decision happened under Jobs, and everything else is just coasting (i.e. repeating the same business success again and again without taking very many risks). Their first custom core design was the A6 in 2012, a year after his death, but they bought the team that made the design (P.A. Semi) in 2008. It took the team about a decade and change to scale up to something that could power a laptop, but the decision was made very early on and was specifically part of the same set of decisions that Apple has been coasting off of ever since. If Apple hadn't bought its own chip design firm they likely wouldn't have remained competitive long-term, in the same way that their computers got really uncompetitive for a few years before every major architectural transition.
Unless by "Apple Silicon" you specifically meant "the decision to transition from x86 to ARM". There is actual work there, but not a lot of risk. Apple famously maintained an internal x86 port of Mac OS X for years after Rhapsody was shitcanned and renamed "Mac OS X Server", so doing the same with ARM isn't that worse. iOS was derived from OSX; and just having iOS already up and running on ARM is already a good deal of the way towards a macOS port to ARM. In fact, it got easier as iOS got more technology hand-me-downs from macOS.