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.
So I went back to the Wiki entry and I made a mistake - There was a footnote about a submersible built by Richard Fossett called the DeepSea Challenger that was first to use the carbon polymer design, which is what the Titan’s design was based on. Anyways, Fossett died before he could use his personal sub, Virgin Oceanic bought it and got it tested (because Richard Branson wanted to use it), but that testing determined that it could only be used once, so they never bothered to use it after that. So I guess the main lesson that Rush learned from all this is to not get the carbon polymer sub tested because that’ll just confirm it shouldn’t be used more than once.
Either way it’s nuts to think that was documented and ignored!