“If it was an accident, their cardinal sin appears to have been not staying with the boat. Hard to know why even at 14 they didn’t know to do that?”
If they were thrown out of the boat in a storm it may have been impossible for them to get back to the boat.
I had a very good friend who thought he was a great sailor and was an investment banker. He decided to organize a sailing trip from France to the Bahamas. They started with 3 100 foot sailboats. The first 48 hours out from the coast of France a deadly wind called the Mistral which brings with it huge waves appeared. All three boats were engulfed and all 25 crew members on all three boats were killed and disappeared. One survived.
The sea can be treacherous.