People that took the power are mostly from the western parts of the Ukraine. That part historically was disputed territory between Russia, Poland and The Austro-Hungarian Empire. Among other things they have different religion - an Orthodox ceremony at the Catholic content.
As I said these people are quite anti-russian, they started Euromaidan firstly requiring to cancel agreements with Russia and signing the same with the European Union. European politicans became a frequent guests on Maidan, supported it. Step by step the situation was heated, in clashes with the police spilled the first blood. President of Ukraine run away. The slogans of the Maidan among other was: "Russian to gibbet" (to branch). In such situation in Crimea started anti-ukranian statements.