The EU which represents majority of NATO countries (with the US and Canada excluded) did. The efforts to get Ukraine to join the EU and then the CIA toppling of Viktor Yanukovych over his refusal.
Then we get the Cremeia response from Russia and this starts the ball rolling.
The CIA did not topple Yanukovych. Yanukovych got over 100 protesters killed and ran away from Ukraine when he understood that he was not going to get away with it and would be facing jailtime. Ukrainian parliament assembled to resolve the crisis and voted 328-vs-0 for holding new elections, which took place a few months later. Not even a single person from Yanukovych's own party voted in support of him.
Countries scared of Russian aggression have been clamoring to join. Russia invaded Georgia and Ukraine twice. They managed to get Sweden and Finland to join up thereby expanding their border with NATO by 1340km.
Truth is Russia could have decided to be Norway if they would have just peacefully stayed in their borders and sold gas/oil to the EU. But instead they decided they would rather be North Korea.
In a decade they will likely be just another client state of China. It is truly sad.