Ships the size of those two vessels don't start, stop or steer on a dime. In tight shipping lanes, it doesn't take much to turn a few thousand yards of clearance into a imminent collision. If the freighter veered off course, there may not have been anything the crew of the destroyer could have done to avoid a collision. The crew of the destroyer could have screwed up royally too. Without knowing what happened, operating off of the assumption that the two vessels were traveling in straight lines and crossed paths, leaves a lot possibilities off the table.