I've also read that the point of the breakup was also where the loungesand smoking rooms were. With the big open spaces, it was a weak point in the ship and at that angle with many other factors the structure couldn't hold up.
The ship reahed it's breaking point, ripped and the bow sank while the stern with air still in it, filled with water, pushing the air pocket to the poop deck. Finally the pressure was to much and the poop deck blew out, explaining some of the major damage to the stern section of the ship.
This is what I've been led to believe.