>>13205183He3 is a lot more abundant on the Moon.
The Moon also has Titanium and other metals.
The point of extracting metal on the Moon and building craft there, is that the escape velocity of Earth is enormous.
Because of the low gravity you can build and fly craft that are way too fragile to ever leave the surface of Earth.
About a third of the fuel to get to Mars from Earth is just to get into orbit. Even if we just make hydrogen and oxygen, that would allow us to refuel craft after the escape from Earth.
The metals would allow to build fancy craft without hauling tons of metal off Earth.
Ultimately the point would be to mine asteroids from Mars. The Moon is mainly a stepping stone to everywhere else.
