Look, i hate to have to be the one to point this out, but the Sailor Scouts are going to conquer Earth just like every monster they've fought against.
There are three main reasons I believe this.
1. They apparently had a utopian society on the moon for thousands of years... yet felt no need to share any of that with Earth until their kingdom was destroyed and they needed a quick evacuation plan. Up until that point our ancestors were on their own.
2. you've got about a dozen teenagers with virtually limitless powers. Sailor Venus already used hers for personal gain. Imagine what's going to happen when they've beaten all the bad guys and Serena and Rei are staring at their income tax forms or standing in line at the grocery store behind some jerk who breaks wind and laughs about it. you've seen them beat people to a bloody pulp for such things without using their powers.
3. We've actually seen the future. The Sailor Scouts do rule the world. Queen "Serenity" and her husband are the unquestioned rulers of the universe and can apparently make more scouts at will. I don't know about you, but knowing governments I doubt they said "let's make the cute blond and her friends our leaders" and more "now that we don't need them to fight monsters, let's disect them and figure out how their powers work". Which leads to MooN Rabbit telling her daughter again about the time Aunty Rei melted 300 tanks like they were made out of butter and crushed China beneith her pointy heel.
Rini: Mommy, tell me again about the bloody march on Poland....
Mercury: What are we going to do tonight?
Jupiter: The same thing we do every night. Wait for Serena to get off her butt and then take over the world!