I don't think a moon base is a requirement, it might help if there is on the moon a mine for Al and Fe that would allow the building of a very large ship more cheaply than using Earth based materials.
But it might be even better to change the course of a comet or asteroid and get materials that are already in solar orbit and need very little pushing to get into Earth orbit.
NASA is planning to capture a small asteroid soon , a large one might have a mountain of Iron in it.