Galileo’s explanation: The following is Galileo’s explanation of why large and small masses (disregarding air resistance) fall at the same rate.
The acceleration of a large falling rock is the same as the acceleration of a small falling rock because a large rock is just a bunch of small rocks falling together.
This explanation is occasionally reinvented by people who think about these things. Though not the first to think this way, they walk in the footprints of the old master!