It is important to understand that Japan, much like most of Europe, was in shambles following World War II. While the United States did conquer Japan in the war, they immediately focused on rebuilding the island nation in a way that was sustainable, so as to prevent any future world wars. Japan became economically powerful and technologically advanced enough to become the economic powerhouse of the region. Because of this, economically weaker nations sought trade with Japan, further empowering the Japanese economy.
Bear in mind, the genesis of this rebuilding effort was happening simultaneously with the beginning of the Cold War. The Soviet Union had imperialist ambitions that sent them to wherever they could gain a foothold. However, much like the Marshall Plan in western Europe (funds for rebuilding infrastructure and national economies), the Soviets simply could not obtain enough influence and fealty of these areas to win out. Instead, the communists focused on economically and structurally weaker Asian nations, such as Vietnam and Korea.
President Truman was very involved in this rebuilding process. He appointed General Douglas MacArthur (who was very familiar with the Pacific theater during the war) to be the Supreme Commander for the Allied Powers. MacArthur's leadership under Truman's supervision helped the Japanese create their own thriving and sustainable business infrastructure that put Soviet states to shame by comparison. Truman vehemently opposed a potential Soviet occupation of the Japanese island of Hokkaidō. Had the United States not established a strong military and economic foothold in Japan after the war's end, it is possible that the Soviets might have interrupted the economic growth taking place on the island.
Ultimately, Japan could be considered "victorious" during the Cold War because they made such a significant economic turnaround, while so many other small nations around the world crumbled. This growth was sustained and gave Japan the chance to thrive rather than live through the Cold War years as an impoverished Soviet state.