Even after watching the video I didn't really get it. One of the comments made it more clear though: On Earth, the orbits decay because the satellite hits the

Even after watching the video I didn't really get it. One of the comments made it more clear though: On Earth, the orbits decay because the satellite hits the atmosphere and slows down, losing energy to drag. On the moon, satellites don't lose energy, but their orbits change. The perturbations of the gravity field cause the satellite to be moving faster but lower on one side of the orbit and higher and slower on the other side. Taken far enough, the low side is lower than the mountain the satellite slams into.