Why were europeans eager to create supranational organizations after ww2?

To prevent future wars and check the growth of communism

Explanation:

In a supranational organization, the ability of nations to affect decisions goes beyond the limit of their nation's borders, they act as a part of a larger body aiming to achieve a common goal for all its members. The European Union and the African Union are examples of supranational organizations.

These organizations create a uniting force between member countries through trade, environmental protection or food production practices,  thereby, preventing war and diverging ideas contrary to the shared value of the group such as communism, which was a threat to nations immediately after World War II.