The Importance of Having a Circular Orbit

Not having a circular orbit tells you that the planet formed and the moon comes from somewhere else. There's a vicinity of a massive object we call the hill sphere, which is the region where its gravity dominates. If an object passes within thehill sphere, it's a candidate for getting captured. The more moons you have and the puffier your atmosphere, the more likely you are to be able to capture an object that comes near you.