Why do heavier objects fall faster?

Whether an object is heavy or light, all objects accelerate at the same rate towards the earth.

That is... @ 9.8 meters per second squared

This means all objects should fall at the same speed, right?

Absolutely!

However, this happens only when there is vacuum

A Scientist named Robert Boyle placed a coin in a feather in a big glass jar and removed all the air from it. Thus, creating a vaccum.

He then inverted the jar and observed that both the objects fell to the bottom at the same time

But this doesn't happen on earth because here the speed of falling objects depends upon their surface area and air resistance

The feather has more surface area as compared to the coin

Hence more air pushes against the feather due to which it experiences greater air resistance and thus,

Hence, the feather falls slower as compared to the coin