I think that the timing is the issue. My guess is once they sort it out, the freighter was going along smoothly till it hits the Navy ship and then has that strange pattern until it resumes it’s path the Tokyo. It makes no sense to suggest that this was in anyway intentional, that the ship was circling looking for a navy ship. In the middle of the night in the complete darkness, does not make sense. Further, nothing from the neighbor he suggested they felt threatened by the freighter traveling up the coastline. I suspect the both crews were simply not paying attention.
Based solely on the video, it appears that the container ship passed close by the warship, proceeded on for awhile. then decided to turn around and intentionally RAM the destroyer.
Again, based solely on the video, no other logical conclusion can be arrived at.