The film centers on Siegfried going from a common man to a noble man. We see that the fluidity of class is impossible during these times, as one must be born into a position of royalty. But Siegfried gains it by killing the Dwarf King and inheriting his kingdom's treasure, and he becomes a great hero by defeating the dragon in the realm. And as Siegfried helps King Gunther to win the hand of Brunhild in marriage we see that the story is about a person's inability to see worthiness in another. Brunhild doesn't see the King as worthy of her, Hagen doesn't see Siegfried as worthy of Kriemhild.
This creates a lack of respect for the position that these people have obtained. And this lacking leads to disobedience and the need for others to please. Primarily, the King wants to please Brunhild and thus he is willing to do whatever is necessary to do so, he only needs the proper motivation which he receives in the form of a lie. Brumhild says that Siegfried took her maidenhood and he believes it. What the King lacks inside of himself--the resolve and strength necessary to fight his own battles--he puts off on other people in order to get what he wants. Now, when he has what he wants he is willing to throw away the good that has been done for him so quickly.
What we see is a lack of true nobility of character from these royal people. Instead, we see the pettiness of people who are used to getting what they want day in and day out, instead be met with defeat. And, this being unacceptable they are unwilling to bend or change in any way. Thus, they become tyrants as they are willing to do anything, including murder, to meet the petty needs they believe they desire.
