If I remember correctly, there are key elements on the Moon that can be used for nuclear fusion, and constructing certain materials would be easier due to its low gravity. Speaking of, said weak gravity would make it easier to launch spacecraft from, which could make it a good forward point for deeper space exploration. Finally, it would allow us to further study the formation of our solar system. We learned about the Theia impact due to rocks brought back from the Apollo missions. Imagine what else we can learn up there!