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.