After reading the map, you will know that, first, Seoul is very close to the 38th parallel. Once the war breaks out, Seoul will bear the brunt, which is really unfavorable. Second, two famous cities in Korea, Seoul and Busan. In the northwest corner and southeast corner, this layout seems to be more important at both ends than in the middle, so it is necessary to open up a new center in the middle, which is economically infeasible (because the Korean economy determines that it must rely on the sea for development), so it is still political. Politics can also drive the development of population and economy.
Sejong City was named in memory of the "great man" King Sejong, who created today's Korea and fought against Japanese pirates. (Actually, it's a big fart. He is respected in Korea and North Korea, and his image is in Korean currency.