Carbon Fiber.... strong and light.. MotoGP and World Superbike type rims,,, Formula 1.. lotsa parts... not meant to be re-used after being stressed... especially F1 stuff... even magnesium motorcycle rims aren't meant for the long haul... the repeated compression and decompression stresses on the sub would have greatly diminished it's strength ... crunch
I have significant experience with carbon fiber and the more you work with it the more you like it. For all the applications you mentioned and in particular aerospace.
This particular application I think was wrong and the design was wrong too. I don't even think they wrapped it correctly.
The most common sub design for this application involves a titanium sphere which is two inches thick. Being a sphere, there are no stress concentrations, basically the stress is evenly distributed. Equally important the material is homogeneous all the way through. With carbon fiber there are two materials, carbon fibers, and resin. Similar to how fiber glass is made, but instead of glass fibers, it's carbon fibers.
The whole design of this sub was just piss poor engineering. The sad part is none of these people had enough knowledge to even question the design.