If the source below is correct, the commander of the Dena ordered his troops to stay on the ship despite the warnings, there was a bit of a mutiny and the survivors are those who rejected those orders and jumped off.
This was a sneak attack outside of an established war zone, for an illegal war, so don’t try to conflate this as an attack on America’s enemies. The USA made them their enemies themselves.
>Established in May 2017 and funded by Saudi Arabia,[1][2][3][4][5][6] it actively promotes former Crown Prince Reza Pahlavi as the next ruler of Iran.