Perhaps it was (relatively) easy. What made it easy was precisely that it was Apple: full & willing integration with the iOS ecosystem. A couple UI clicks/taps, if not outright automatic, and your AirPods are happily talking to the device you want to hear from.

All competitors have to cope with interface limitations and API inadequacies. Even one extra obligatory UI step can practically ruin the experience (as compared to AirPods).

Getting to the point where deep integration is easy ... is hard.

Including the W1 and H1 silicon?

Given that the man is an analog extraordinaire, there shouldn't be any reason for them to hire him for anything but that I believe.

Are you saying the H1 and W1 could have been designed by a lower tier OEM?

Yes, that's a walk in the park ASIC

Odd that nobody did it before Apple.