If you read the report that is linked above, you can see the relative speeds, headings and impact geometry. The McCain crossed in front of the cargo vessel and

If you read the report that is linked above, you can see the relative speeds, headings and impact geometry. The McCain crossed in front of the cargo vessel and was hit in the aft section by the cargo vessel that had a constant speed and heading. You don't stop or turn a cargo vessel as quickly as the McCain can maneuver. You also need to take into account that you don't shove a ship sideways through the water easily - it can't slide as easily as a car can. The majority of the cargo vessel's kinetic energy will go into plastic deformation. It's not a sudden impact, more a crushing and deforming. Edit: I have to revise what I said about the impact, according to the report, sailors close to the impact likened it to an explosion.