Two things:
First thing: We don’t know for 100% the carbon fiber portion failed first. It could have been an end cap or a window. If I had to bet my life it would be on the carbon fiber failing, but it’s not absolutely certain at this moment.
Second thing: Where the sub wreckage was found was, according to what I’ve heard, right where the sub was headed. So why did it take several days for that area to be scanned? Why didn’t they START where the sub was supposed to be?
Not having arranged anything ahead of time, it took several days to get suitable equipment to the site. One is a French robot and another is a Canadian one. Not many things can go that deep.