Also, it imploded. Carbon Fiber (which is an impregnated plastic, it needs to be noted) isn't suitable for that type of task. The fact it didn't implode the first time they went down just shows they got lucky. That thing would have needed to be stripped and xray scanned after every trip, but they sure as hell weren't doing that. They were cutting every corner they could.
The company also fired an engineer because the observation window they were using was "off the shelf" and only rated to 1500m or so. They were going down to nearly 4000m. They didn't want to hire any subject matter experts (the dead CEO said "old white guys" and he died for his stupidity) and 5 people are dead for it. He was trying to be Underwater Elon, completely ignoring that SpaceX works because they went on one of the most epic expert poaching sprees in aerospace history. If anyone remembers the early SpaceX launches, that old guy commentating is the most successful controller in human history.
As for the submersible, it imploded at 2000m or lower. I saw a time to failure suggesting in the microsecond range. Everyone is dead and in a million bits on the ocean floor. The submersible has multiple, redundant ways to surface. They've been dead since contact was lost.