Read an article years ago that the fire was deep in a coal bunker against the hull. Some evidence that the steel in the hull had too much carbon in it and combined with the heat of the fire made the hull in that area very brittle. Given quality controls for steel production were not exactly what they are now, entirely plausible scenario.
I remember decades ago in a town i grew up in in northern Michigan, there was a tannery on the shore of Lake Charlevoix and a dock where the coal freighters would unload the coal for the tannery.
If not used on a regular basis, the piled up coal would start to spontaneously combust in the center of the pile and start smoking. To get around that, they would frequently bulldoze the piles to prevent the build up of heat.
That's one theory on why the USS Maine blew up in 1898 - coal bunker with the same problem right next to the magazine.
It’s also been said that the steel used was salvaged from another ship which caused it to be brittle.