Why did having the soveit union as an ally contradict one of the reasons for the united states involvement in the war

The cold war. United states and soviet would build bomb to show off their country was stronger. After a while it ended. But then world was came Nazi and there became the aggression with the soviet. They didnt like the nazi so they grouped with US. Then they used the bombs on Nazi.

My understanding of bad worded history books

the correct answer is “opportunity cost”. opportunity cost is what a company misses out because it decided in one option over another one. in this case, the company decided to invest in building a factory so it gave up another possible benefit or profit in order to achieve success with the factory.  

trade-off is not the correct answer since it is a situation in which you accept losing something in return for benefits in other areas.

and finally, consequence is a general term used to accept what it comes when you make a decision. it can be a positive or negative consequence depending if the decision you took was the correct one.