[clairity]

spacex, as far as i can tell, is a research company that launches satellites to fuel its space exploration research. the research side couldn't stand alone, as that's not a viable business in itself, so the satellite business is really the core "business" here. the making of rocket engines could possibly be outsourced (or turned into a separate business), but those customized engines are integral to its competitive advantage in more efficiently sending satellites into space than its competitors (and in sending people to colonize mars, its long-term mission). core competencies like that aren't separate businesses; they're the business itself. if spacex decided to write its own accounting software and then sell it to others, then you'd have a breach of the single business focus.

apple, however, is in something like a dozen different businesses that are completely viable as stand-alone entities that don't gain much from being consolidated (brand value, for instance, can be franchised if a unified brand face is desired, like mcdonald's does). incidentally, apple wasn't a hardware company that morphed into software, but rather, it was always a computer marketing business (then more broadly consumer electronics, and now encroaching upon consumer entertainment). nest is a good example of what a spin-out company in an apple breakup might look like.