My guess is that this accident was probably uncontrolled flooding in the forward torpedo room leading to a main battery failure then implosion. 2nd guess, hot battery in those old torpedos caused an explosion in the tube or the sub itself. Then implosion.
a lot of bad things could have happened but they recorded no implosion, so that would indicate flooding
torpedo’s do not use battery’s but they sound like electric razors on sonar, inner torpedo door is never opened before the outer door and the tube is flooded, still... why no implosion?