The unsung part of this is that Bluetooth is a ridiculously complicated protocol. Basically everyone has a broken implementation of it. If someone asked me to choose whether to write either a C++ compiler or a bluetooth stack, I would probably choose the C++ compiler.

There are very few people who are both passionate about the problem of wireless devices and who understand all of the stack enough to make a driver that is fast, resilient, and standards-compliant. I hear that Apple sometimes bends the "standards-compliant" part - which is why their airpods only work with their devices.

Apple has done a great job giving this team of <100 engineers the space they need to succeed, and it's a huge feat. Most other companies don't even try to write their own BT stack (for good reason) and just use a vendor solution, so their user experience is subpar.