How does Sougo become Ohma-Zio?

During the entire series of Zi-O we are shown that Sougo becomes a tyrant king who takes over the world, becomes power hungry, and is also a ruthless killer. But what sets him down that road when it's shown he doesn't have anything in common with his future self besides wanting to be a king. (Which still doesn't make sense for the series for being told you can become a king after your parents just died by some random person and that somehow becomes your whole personality.)