The main reason why Putin got pissed is because Russia surrounding by Nato and allied of America. Now Ukraine want to break away from an old Guard Russian and make even more Pissed to Putin. Plus President Obuma is ways too weak in foreign policy that's why Putin do what he please by took Crimea back to Russia.
Crimea is very important Base for Russian Newclear fleet to the blacksea for Russia, So there's no way Putin could lose the Crimea to the Ukraine...
As you all know, when Bush Jr was in the White House. there's no Dictatorship like Kim Jung Il, Gaddafy, or Assad came out and blackmail him like they did to Bill Clinton and Bullied Obuma.