Probably that carbon shell was going to fail after so many deep dives.
I wonder what sort of inspections and maintenance were performed between dives.
I wonder who will investigate OceanGate? Navy, Coast Guard, NOAA, NTSB, or FTC? Some agency I’ve missed? All of the above?
This sub was some sort of multimaterial Frankenstein which used titanium as well as carbon.
Titanium is also subject to creep fatigue. It was an issue with the USSR titanium subs.