Two moons once orbited earth
After the big splat that formed the ring of debris from which the moon coalesced, a smaller moon formed at a Lagrange point while the main moon formed. The two then proceeded in lockstep for millions of years. But as tidal drag slowed the earth’s rotation and the moon drifted outward (conservation of angular momentum) the Lagrange point ceased to be a stable orbit. The little moon drifted out of position, just as our recently discovered sidekick Trojan asteroid occupies an irregular orbit that stays more or less in the vicinity of its Lagrange point.
Eventually, big moon and little moon collided. And that explains why the near side and the far side look so different.