Both the lead actresses have some other life fantasy, and they get something else out of life. The inner court, society, family, and war field is a journey of thinking to establish a balanced state by passing/opposing all these. There are similarities in the story, I will not spoil the story by telling those similarities
More then anything, because of historical facts. if you got interested in historical events from Scarlet Heart, you should give it a try ( like I did). This drama takes time just after Gwangjong's reign, and starts with story of Gwangjong's son, Gyungjong. There're some more couple of characters that you will recognize from Scarlet Heart.. As well, all the tragedies start because of the battle for the throne...