Question

Why potted plants die when over watered

Answer 1

Because there is no more space left for the air to come in , as water occupied all the space.
The potted plant is unable to take the air from outside through its roots .

Hence the plant dies

Answer 2

The roots of a plant absorb air ,water and nutrients to ssupport the stems and leaves above.
execessive watering cuts off the air and the roots begin to suffocate,rot and eventually die.
the most common of overwatering r wilting leaves and a pot that feels heavy due to soggy soil.

hoped helps..