That is precisely the problem. There was no internal conflict before the CIA began supporting the Ukrainian opposition.
This is what Putin wants you to believe, that Ukrainians were living happily under a Russian puppet, but somehow they revolted because of Victoria Nuland.
The revolt would have happened with or without Western support, because people were fed up. They wanted Ukraine to joint the EU, and Yanukovich refused to move the country in that direction.
Ukrainians wanted change, and the pro Russian dictator prefered to kill his own people rather than stepping down. In the end, he fled to Russia. This is how legitimate he was.