I have zero doubt the incident was caused by negligence. I was in that area and the swells were forecast. I don’t however understand why his insurance is not valid. The main reason you have insurance is to protect yourself when you do stupid things which we all do at one time or another. Can your auto insurer deny you coverage if they find you were using your cell phone prior to the accident? The only thing I could see is that he took the boat out when it was not in a sea worthy condition with the failed steering.