It's true that monopolies can invest on R&D like no one else can because they don't have to compete on price. Waymo probably wouldn't exist if it weren't for Google's absurd profit margin.

However:

1/ There are obvious downsides to the lack of competition.

2/ In this case, the proprietary protocol that AirPods use is not revolutionary R&D, to say the least! Any competent software engineer can create a new protocol superior to bluetooth if they can drop compatibility with bluetooth.