Answer:
1. Because of diffrent political belifes. (We must remeber that the soviet union saw capitalism as a disgusting foe, and the United States saw Communism as a form of tyranny.)
2. To elminate a national security threat near the homland. (This is because this was the cloest communist nation next to the united states, with ties with the Soviet Union and had the power to launch nukes at the homeland. The main way to fix this would be cutting the head off the snake {aka killing castro})