I mean…. It sounds like the insurance company knew it was going to flood. Being close to a body of water has nothing to do with likelihood to flood…
Seems like your friends should have moved before the flood, if they couldn’t get insurance for it. Why were they even searching for flood insurance if “they weren’t particularly close to a body of water”?
Sorry but this definitely sounds like your friends’ fault. They knew they needed the insurance because it would flood, the insurance company knew with high certainty it was going to flood, and then it did flood.