Two pilots were on board. Apparently there were issues with the ship's propulsion system at last inspection. My money is on a mechanical issue; if not, this was a monumental fuck up by the harbor pilots and/or the crew.
edit: lol, I am pleased with how this comment has aged. Yes, it was a power loss. Quick thinking and action saved lives. Bravo. Now it remains to be seen whether deferred maintenance or similar negligence were to blame; if so, people need to pay up.
They evidently called Mayday before colliding. But if I was asleep at the wheel and woke up to see a bridge coming at me, I’d probably let yell Mayday too.
I watch commercial shipping all day out my office window, almost all tugs are used to just move the ship away from the wharf, something on the order of a boat-length.
I don't know what the layout of the harbour in this incident, but the boat could have been kilometres from the wharf where it docked.