I doubt they considered it risking their lives the way most of us do. The Polynesians were expert seamen and navigators. They knew how to build boats, provision them, navigate by the stars, and find tiny atolls across vast seas. Sure, sailing has inherent danger, but if you're an expert, the risks are not insurmountable. Even today, many people sail across entire oceans alone in tiny 27' sailboats. Some guy just sailed from England to Argentina on one to return home for his dad's birthday when he couldn't get a flight. One man's deadly risk is another man's adventure.