Why did Russia start its aggression against Ukraine after the Ukrainian unrest from 2013-2014?
There're still different opinions on the level of Russian participation in both the Crimean 2014 crisis and the East Ukraine's military pro-Russian unrest (2014 - now). But, if we admit (as I do) that both of mentioned problems were planned and implemented by Russia, why did that happen at the very moment after president Yanukovich fled the country?
I see two possible answers here:
Everything was planned by Russia long time before and the victory of Kiev's protesters was the occasion for this. If yes, so why this happened in 2014 not in 2004 — after a similar victory of Kiev's protesters?
Nothing was planned beforehand, but the new authorities, that got the power after Yanukovich fled, posed a thread to Russia (NATO, EU etc.) and Russia started to protect its interests.