I remember seeing a claim that the Bluetooth part was a feature since you could just "pass the controller" inside the cabin but I haven't been able to find a source for it.

As for the carbon fibre:

>OceanGate CEO Stockton Rush says the company had been evaluating the potential of using a carbon fiber composite hull since 2010, primarily because it permits creation of a pressure vessel that is naturally buoyant and, therefore, would enable OceanGate to forgo the use — and the significant expense — of syntactic foam on its exterior. So, for Cyclops 2 OceanGate decided to avoid the metallic hull altogether and began a search for a manufacturer that could help it develop a composite hull.

https://www.compositesworld.com/articles/composite-submersib...