Why were free elections not held in Korea and the countries of Indochina in the 1940s and 1970s?

Free elections were never held in Korea due to the fierce rivalry between the United States and the USSR. Formally, according to international agreements, after the withdrawal of foreign troops in the country, general elections were to take place. But in fact, neither the USSR nor the United States wanted to yield to each other. The goal of the USSR was to entangle the whole world with the communist web, and the goal of the United States was to resist the communists with all its might, at all costs. Therefore, Korea simply split into two states: the Democratic People’s Republic of Korea (DPRK) in the north and the Republic of Korea in the south. Free elections were also to be held in Indochina. This concerned South Vietnam, Cambodia and Laos, but the elections were never held, power was unconditionally transferred to the communists. Because the USSR, China and the DRV, during the protracted war in Indochina, even contrary to the agreements, continued to support the communists from Laos, Cambodia and South Vietnam. The same cannot be said about the United States, where after the resignation of President Nixon, aid to the allied regimes in Indochina was sharply reduced.