Sounds like it was (shocker) really well designed. It even sank once when a cable snapped on support boat --- crew escaped, and it was recovered and retrofit. And if things go sideways, the cabin/titanium sphere could detach, floating freely up to the surface.
After hearing about OceanGate, deep sea subs sounded terrifying --- but reading about this is somehow very comforting.
i'm still fine with using a game controller for a project like this. game controllers are designed to be sturdy, ok with abuse, replaceable and adaptable.
That said, a 15 year old, $30 controller might not have been the best idea.