Think about it. Loki has been blessed with this grandiose lifestyle, and yet still, he places himself in the shadow of his brother. He's insecure about his place in his family, in the world. He strives to be accepted, but is consistently given reason to believe he will never equate to his brother. Add insult to injury, he discovers his place of origin is completely opposite from his so-called family's. He's been told all these years to fear these species, to fight them, and now he learns that he IS one of them. He can't really find another outlet for his emotions, so in the interest of 'vengeance' - maybe more of an attempt to dominate and take control of his purpose - he crowns himself king. And, of course, all hell breaks loose.
I think the story is heart-wrenchingly beautiful, in its exploration of insecurity, destiny/purpose, and what can occur if you lose your personal identity. Is this just me? Am I over analyzing things?

