Film director James Cameron has expertise in designing and testing these submersibles, and he has many criticisms of the design of the sub that imploded, and of the hubris of the CEO who ignored repeated safety warnings from the diving community. He also mentions that the sub seems to have been attempting to resurface when it imploded, suggesting that they were aware the hull was starting to fail.
He’s pretty involved in the deep sea submersible community by all accounts, supposedly he’s dived to the Titanic site 33 times and been involved in the design of some of the vessels used.