I am a former US Army officer. There is no maybe about it. It is a war crime. Even if you can justify the sinking of the ship you can not justify the abandoning of the sailors in the water.

They only have to rescue if they can and don’t get in danger of being sunk themselves. There’s a reason a submarine was operating in this area and not a surface ship. Iran has plenty of anti ship missiles of different kinds. Submarines have zero defense against these. A submarine on the surface conducting major rescue operations for hours is sitting ducks.

We don’t know enough about the tactical situation to pass judgement.