Why aren't we get crushed by the weight of Earth's atmosphere ?

 The mass of a cylindrical column of air is 754 kg.

This much atmospheric pressure acts on our body   !!!!!

Why aren't we get crushed by this much weight exerted on us  ????

We are not crushed by air pressure because our body has evolved over time to withstand the pressure.

The air inside our body is at essentially at the same pressure pushing outward.

This makes the pressure forces, balanced.

This internal pressure from our body is the main reason why we can not travel in space without a space suit.

The pressure in space is essentially zero.

Without the air pressure pushing down the body, the internal pressure inside the body would make the body to inflate like a balloon.

This will go on until the pressure is released.