Everything is impossible until someone does it for the first time.
It’s not impossible. We will need to invent a process other than Kroll or Cambridge to do it, is all, a process that uses lunar materials and solar power.
One we humans have a permanent base on the moon, then real development can start. We do need to work out the basics before we go.
One very useful thing will be a means of storing He3 until someone learns how to burn it in a fusion reactor.
The Moon would be the perfect place for a beanstalk launcher, then we can go to Mars and set up a mine or two there, with a Mars base/beanstalk used as a launch point for asteroid mining.