Carbon fiber has a high strength to weight ratio in tension. In compression, well, we found out.
It sounds like it’s possible the viewing port in front which was not rated for the Titanic depth could have failed and then the rest crushed apart too.
Did I not read that the ?acrylic viewport was seen by passengers/crew to be visibly deforming and buckling inward and outward under the pressure strain on previous dives but the craft continued to be used anyway?
Which was stronger — the carbon fiber or the glue that held it together?
Sometimes things that appear to make no sense actually make no sense.
I wouldn’t be surprised if the failure was associated with differential flexing between materials, or corners.