The thing the Moon is genuinely rich in is oxygen. Lunar dirt - regolith - is something like 40 to 45 percent oxygen by mass. Almost half the ground is oxygen, locked up in rock. And oxygen is the heavy majority of any rocket's propellant load - when you fuel a rocket, most of the weight you're loading is the oxidizer, the oxygen, not the actual fuel. So if you can pull oxygen out of lunar dirt and fling it into orbit with a catapult, you've built a gas station in space. Every spacecraft passing through stops getting refueled by stuff hauled up from Earth and starts getting topped off with lunar oxygen launched for the price of electricity using a mass driver. $SPCX
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