If the ship was at anchor, then would it not be at anchor where the harbor authorities told it to anchor? And wouldn't the captain assume that the harbor authorities knew what they were doing when the told him to park there? So why would the captain be at fault?
It will be interesting to find out more details. Typically, when a ship is at anchor, the quartermaster watch takes a round of bearings at regular intervals to check on anchor drag.
Plus, any GPS unit on board this vessel would have an anchor drag alarm...heck, any cheap marine GPS has this alarm feature.
You’ll probably get 8000 replies that say the same thing; the captain has total responsibility and is always at fault in any incident. I was on a ship that had a collision with another Navy ship. Both captains pretty much immediately relieved.