Kumwa is so cruel now and power hungry. It isn't even about the people anymore. He'd rather be the ruler of a tortured nation than let it all go to join Jumung for the benefit the people.
Self interest, hunger for power, greed, anxiety and self assurance, this is very common up to this day. This is just a reflection from the past in what we are all experiencing at present. Be it from the smallest unit as our own family.