Hopefully, the vehicle was not in trouble before the disintegration.
I like thinking the entire crew was excited and thrilled, then, poof, dead in the blink of an eye.
I am surprised the craft did not have a data recorder that would jettison and float to the surface.
That would create a much smaller search area, and the surface crew would know exactly what was happening at the moment of release.
That will be a feature on their next model
I had a feeling that when they lost communications, which was to be expected, but only for a very short period of time, and never regained it. It was around that time the sub experienced some catastrophic failure.