Why did separate governments form in North Korea and South Korea in 1948?

The division of Korea into two separate governments in 1948 was a direct consequence of the geopolitical tensions of the Cold War following World War II.1

After Japan’s surrender in 1945, the United States and the Soviet Union divided the peninsula at the 38th parallel as a temporary measure to accept the surrender of Japanese forces. Efforts to establish a unified Korean government through a Joint U.S.-U.S.S.R. Commission failed due to irreconcilable disagreements regarding which political groups should be consulted.123

Consequently, the United States brought the issue to the United Nations, which called for general elections. While the South held UN-observed elections in May 1948, the Soviet Union barred the UN commission from the North. This led to the formation of two distinct regimes:3
* South Korea: The Republic of Korea was inaugurated on August 15, 1948, with Syngman Rhee as president.3
* North Korea: The Democratic People’s Republic of Korea was proclaimed on September 9, 1948, with Kim Il-Sung as premier.3