Whose fault was it that the titanic sank?

there are alot of arguements of whose fault it was. It could be the look outs who didnt see the ice berg until it was too late, or the captain for goin to fast at night. a regular cruise ship today goes 25 knots and a ship back then only went 20 but the captain had it set at 25 in the artic cold which is stupid. was it the workers didnt work hard enough to get the ship to turn? or was it just dumb luck that the owner of the ship said it was unsinkable? what are your thoughts?