My understanding is, the bow descended at a slight downward angle which caused her to dive forwards and some distance away from the rest of the ship, and when the bow approached the seabed it ploughed into the sand at a forward angle, digging and compressing her bow in as she skidded forward in the sand until she came to a full stop. Perhaps the impact caused the support columns in the broken end to fall which caused the decks at the back to fall.
The bow was also fighting against the current which pushed the coal south of the wreck as it descended. The currents probably slowly down the speed of the bow's descent as it journeyed northwards before her bow made contact with the seabed.
Titanic sank roughly inside the red circle. The coal was carried south by the current and the bow travelled north and probably ploughed bow first into the sand.
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