Here's why:

* Inertia is the tendency of an object to resist changes in its motion. The more massive an object is, the more inertia it has.

* Mass is the amount of matter an object contains. The Earth is significantly more massive than the Moon.

Therefore, because the Earth has a much larger mass than the Moon, it has more inertia. This means it takes more force to change the Earth's motion than it takes to change the Moon's motion.