For starters this is untrue. It is the point of view the people had till few hundred years ago about the Solar System though. From there perspective the Earth was the center of the universe, and also the biggest body, so all the others were orbiting around it. So going by that assumption, for that to happen in practice, the Earth should be the biggest of all bodies in our Solar System, to have the most mass by far, thus having the strongest gravitational pull by far, so that the other bodies orbit around it, like the Moon does in practice.
