Noah was fully aware of the path to salvation. That is exactly why He built the Ark.
Moses was also fully aware of the path of salvation. That is exactly why He was given the Commandments. Do you think Jews were obsessed by following the commandments because they thought it was a nice thing to do? A cool and fun way to live their lives?
They suffered to follow the commandments, and they were happy to suffer because they knew it was the path to their salvation under God.
Have you heard of the concept of "kareth" if a Jew does not follow the commandments? It is the opposite of salvation.
