One would think that if they didn't understand Physics. The broken pieces would continue to maintain an orbit around Earth. Perhaps the moon debris was pushed away from the earth during its breaking or, better yet, pushed in the direction of the orbit. Given a rotational velocity, the pieces would continue to orbit our planet, rather than crash into it. Some pieces would crash earthward but most would be drawn together due to gravity. Eventually, the moon pieces would coalesce into a sphere again. Although not mentioned, I'm sure part of the destruction that occured on Earth was due in part to deep imapcts of lunar material.
Too basic. Yes, you're right as a matter of physics if they all maintained a similar distance and rotation, it would continue to orbit. But that's also two dimensional thinking.. in an explosion which would shatter the center of an orbital mass, debris would move in all 360 degrees, some away from the earth, some toward the earth. But the moon as shown moved apart only in seemingly two directions.. also, while they would maintain rotation with earth, we have to remember that each mass would maintain it's own establishment of gravity, and so they would have a high propensity to slam back into each other as much as anything until order was established. This is what we think created the belts on other planets. So, the fact that they just stayed at a set difference from each other separated only on one axis really I couldn't figure that out.
It's just a science nitpick.