I would think that the Sub captain is more to blame, unless they were running on the surface, and even then, he’s the stealthier boat.
If the sub was on the surface then he was not the more maneuverable vessel. Think about it. Submarines do not have a keel & so they have some directional instability while cruising surfaced.
There was another collision involving a surfaced sub a few years ago. The sub was cruising a parallel course while re-supplying from a large supply ship. The 2 vessels bumped when the sub side-slipped into the larger vessel.
Not enought to go on in this story, but if they were surfaced I could see this happening very easily.
As I teach my children on our boat.
1. Nothing happens fast on a boat. (If it does it’s an emergency)
2. Never hit another boat.
The sub may move faster but the surface target can call tonnage!