I think that guys like Jony Ive have a ton of side projects along with their normal work load. "Deeply tired" may be 100% true. Rich people get burnt out just like the rest of us. Then add in all the flights to Hong Kong, London, Shanghai, Israel, and everywhere else your designs are being built and tested. I mean, jet lag is real! I'm not trying to make excuses for the guy, but "tired" is an apt word for most wealthy business execs. They don't get where they are by chasing skirts in the Bahamas. They get there by working 16 hour days for years!
Most of the wealthy people I have met are exhausted by the time they reach retirement. It's hard work! We only see the cutesy photos the media spreads about; we don't see the real world hours worked by many of these people. At some point even the super-charged, highly competitive types who are willing to destroy themselves for fame and notoriety will burn out.
I don't blame him for leaving; starting his own low-stress design firm. Sit back while clients run to him and his team and pay top dollar for "My new chair was designed by Jony Ive" crap. Sounds like a pretty sweet deal. The guy has "Norman Rockwell" superstar fame and will get whatever price some Hollywood plastic surgeon is willing to pay for that exclusive 15,000sf "Designed by Jony" home in Beverly Hills.