It's really interesting how the historical strengths of companies can persist even after decades of evolution. If the people are coming and going, how is this institutionalized success being cultivated and maintained?
To be honest I don't know the answer to that. That said, Apple has always had corporate value of being maximally responsible for their own destiny. It's hallmark card wisdom to know the things you can change and accept the things you can't change, but in Apple's case their history has been filled with finding things we can't change and replacing them with something we can. So where one company might say "Well we have to work with what ever the microprocessor company will agree too" Apple wants to say "The microprocessor company will do what ever we require of them." And if they can't find such a company they look at becoming a microprocessor company.
A lot of that thinking was laid out fairly extensively in the lawsuit over manufacturing sapphire they got into. The manufacturer (GT Advanced) complained (reasonably I think) that Apple's contracts were so onerous as to make them employees of the company in everything but name. And that appears to be how Apple likes it, complete control of their destiny when ever possible.
At least part of it is that the people aren't coming and going.
When new, key players arrive they're attracted and vetted by the existing community. And that community is well populated with folks that have long tenure.
There are plenty of folks at Apple in key technical positions with 10+ years at the company, and not a few with more than 20.
Apple isn't going down this road again because it's "in their culture", they're doing it because it puts them at an advantage and because they can. Changing the architecture means changes from the silicon level to the application level; it's not so much about engineering talent as it is controlling the entire stack. Still, 30 years later, Apple is the only company that could pull it off.
There has to be at least a little bit of culture having an impact here, even if only in the sense of people being able to say they've done a wholesale change of architecture before so they should be able to do it again. Also the culture of being responsible for the entire stack including hardware, OS, and software gives them a lot more flexibility than somewhere like Dell where they'd have to go through extensive negotiation with Microsoft to make a change to CPU architecture fly.
My guess would be that such specific historical strengths are local manifestations of a more general instinct that is nurtured within a company culture. This instinct would result in similar behaviour when presented with a similar situation — for better or worse.
I also suspect that a company like Apple would have a portion of employees that stick around for the very long term, who have been there since early days and can act as the company's institutional memory.
Specifically in this instance though, it's pretty clear that Apple is going down this road because they've already started going down this road. This is all just straightforward technology and skill reuse: the touch bar is pretty much an Apple Watch in a different package.
A lot of that thinking was laid out fairly extensively in the lawsuit over manufacturing sapphire they got into. The manufacturer (GT Advanced) complained (reasonably I think) that Apple's contracts were so onerous as to make them employees of the company in everything but name. And that appears to be how Apple likes it, complete control of their destiny when ever possible.