Let me start with the caveat: I am not an engineer, nor am I an expert in hydrodynamics.
My thoughts start with the fact that we do not know for certain what the damage to Titanic's hull was, whether or not there were any bulkhead failures, and whether or not there was any significant damage to Titanic's double bottom. For example, while the 'grounding theory' is not currently in vogue, there is the often overlooked and unexplained flooding in boiler room four, where the water slowly came up from the floor over the plates which made up the ceiling of Titanic's tank top (the top portion of Titanic's double hull).
That being said, it is my understanding that Titanic's design, in large part, is responsible for her lack of capsizing in as much as she was built with only vertical bulkheads. Meaning, as each section, or compartment, flooded, the water was able to spread itself horizontally without much impediment. This is distinctly different than many modern ships (and warships) where ship bulkheads spread horizontally as well as vertically. In most scenarios where flooding is limited to a small section of the hull, having horizontal bulkheads allows for areas of flooding to be isolated, thus preserving important spaces (and the equipment in them) in areas adjacent to the hull breach; that being said, when horizontally separated spaces along a large section of the hull are breached, absent quick counterflooding, the additional weight of the water on that single side of the ship can very quickly cause a ship to roll.
Again though, take my comments with a grain of salt! As I said I am no engineer.