You are conflating 'assisting us with criminal investigations' with 'owning up to a criminal act and returning stolen property.' The treaty you keep referring to has nothing to do with criminal acts committed by the Russian government itself against us.
Oh, by the way, the Russian government and whoever else who has Hillary Clinton’s emails did not steal them from the United States government. Hillary Clinton’s server was not the property of the United States government, and was not part of the official communications system of the United States government, and was in no way authorized for such communications. It was the property of Hillary Clinton. The “crime” committed by Russia (and every other intelligence agency in the world) was not against the United States. It was against Clinton personally.
That’s why her security breach was so bad.