The leaders were just too greedy for personal power. The conflict between North and South was between a 'single young ambitious' leader and 'multiple old greedy' leaders. Kim Il Sung was gathering popularity every day and the old greedy politicians in the South were getting old every day. The old greedy couldn't wait any longer. Before withering away, they had to hold some high positions so that their names could be recorded on the history books.
Tigers leave their skin after death, but men leave their name after death.
Koreans view their clan as the center of the universe and each individual's life is a part of the clan. That is why leaving one's name behind is so important. The problem is what kind of name to leave. The yangban class was a counter-balance to the kings and existed for centuries through various dynasties. They enjoyed poetry while farming.