Why did Fidel Castro become friends with the Soviet y ion

Fidel Castro was a communist

Explanation:

Fidel Castro led a communist revolution in Cuba and so his natural ally was the most powerful communist country in the world, the Soviet Union.

With Cuba's proximity to the United States, Castro and his regime became an important Cold War ally for the Soviets. The relationship was for the most part an economic one, with the Soviet Union providing military, economic and political assistance to Cuba.