That corruptionist was not "overwhelmingly popular". It was of the political party that is popular, not more not less.
It was all orchestrated by Russia. You can find tons of videos of russian hero's of that time, and they openly confirm now, that regular military was in Crimea, Donetsk , etc, since 2014. This is not some "leaked" phone. It's many interviews openly sitting on youtube and confirming with smiles their actions.