So many factors contributed to the loss of life that it's hard to pin fault on any one person or group. Certainly the captain exhibited terrible judgement, and there were definitely not enough lifeboats.
Another part of the blame apparently rests on the shipyard that built the Titanic. Much study has been done on the samples that Ballard retrieved from the Titanic's hull, and the ship's materials and design seem to have been a factor in the sinking of the unsinkable. Steel from the hull has been found to be of an inferior alloy and quite brittle, and rivets that held the plates together have a lot of slag incorporated into the metal, making them much weaker than they should have been. As a result the gash, which should have been able to be contained by closing waterproof compartments, resulted in major hull buckling, rendering the compartments useless and leading to the sinking of the boat.