The only cause of the sinking I've even come across is aerated coal-dust touched off by a broken electrical cable. Since the engine room was pretty much surrounded by coal bunkers (they ran down the sides of the ship, between the hull and the engine room, ironically to protect it from impacts flooding the lower spaces very much), this is actually pretty plausible.
Compression & heat from the torpedo detonation could have ignited the coal dust. Folks examining the hole which likely sank the ship claim it has characteristics of a detonation from inside one of the coal bunkers, or two detonations, inside and outside. Roughly 200 kg of coal dust & small chips would have had the energy to bend the hull plates outwards & shatter or damage the internal bulkheads.
Surviving bridge crew reported the Captain gave two orders after the detonation. The first was to turn Port towards shore, the second amounted to continuing at same speed. This would have had the effect of forcing water into the hole in the coal bunker placing pressure on the weakned or damaged internal bulkheads and flooding the adjacent compartments faster.