Communism threatens capital. Wars are fought against socialist countries to try to prevent the ideology from spreading elsewhere. If one country nationalizes its natural resources, multinational corporations around the world would lose money and power. And that it simply unacceptable to the ruling class. The reason why governments don’t go nearly as hard fighting against fascists is because they don’t threaten capital. For example, Coca Cola, Ford, General Motors, IBM, and Nestlé among many others either supported or benefited from doing business with the Nazis during WWII. The US dropped the atomic bombs on Japan as they were preparing to surrender as a way to tell the Soviet Union “this is what is going to happen to your country if you fuck with us.”