The father wanted so badly to be a great swordsman but no matter how hard he tried, he could never reach that level. Dorian being a prodigy and reminder of his wife turned him into an abusive asshole. Had things been different, maybe he wouldn't have been so sad.
Also, I like how Robert doesn't care much about the <Golden Throne>. It's his strongest blade but in the end, it's just a tool. He came to the war for a challenge, not an item.