I think it most likely did so if it went dark you either have a complete power failure or the thing got crushed like a crisp packet.
I am 100% sure the people who built this thing know exactly what happened already.
If the sub had different forms of communication and were all on the same power source then you have the plausible conclusion that the thing could have lost all power. If each form of communication was on a different power source or even switchable power source then an implosion seems far more likely. This is all theory and conjecture obviously but once you know how the thing is built you can put together a picture quite easily. At least I would hope so.
yeah was also thinking if leak no chance to react if sudden, think full investigation will tell us what kind of safety/backup measures it had in place something tells me its not gonna be good