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.