Why did the Soviet Union depart from the former Allies? WWII

The relations between the Soviet Union and the United States were strained.Relations after World War II between the United States and the Soviet Union deteriorated into cold war because the two nations had radically different ideas of how the post-war world should be configured. ... For him, keeping Soviets safe from another attack from the west was of paramount importance.

Explanation:

when a country suffers, for example, a drought period, the market product is affected for a low offer, in this case, potatoes; the government has to tax to the households, which have to give more money for the potatoes which they consume, that situation make them consume substitute goods even through loans, it could increase the financial market movement and the inflationary phenomena, the business has to increase salaries in order to the employees could buy a more expensive food (potatoes) and in order to inflation tha business had to buy expensive supplies in the factor market, while the rest of the world have to gain more money to consume the same amount of potatoes.