The russian majority was engineered, in living memory, at the cost of others who now have no voice in this.
I think you'll find that ethic Russians formed a majority in Crimea even in 1944. The Russian tsars ruthlessly suppressed Ukrainian nationalism, that's one of the reasons why so few speak Ukrainian in eastern Ukraine (western Ukraine wasn't part of imperial Russia)
Indeed the whole of Ukraine has been the subject of continual ethnic cleansing and engineering. Ukraine was the birthplace of the Russian nation and Kiev was the capital of Russia hundreds of years before Moscow was.
The reason Ukraine has turned out ethically different to the rest of the Russian hinterland is because its geographical position has meant that it provided the territory for the clash of empires/civilizations/cultures/religions, including muslims, catholic, and eastern orthodox. I believe that Ukraine means "borderland" presumably alluding to the fact that it it represents the division between east and west, even today ?
But whilst there is clearly a sectarian dimension to the present crises in Ukraine today, after all one of the first things the coup leaders did after seizing power was to repeal the law on regional languages and made Ukraine the sole official language (they later backed down under strong pressure from their EU backers) I suspect that it would be over simplistic to put it all down to narrow sectarianism.
It is perfectly feasible for someone who is not an ethnic Russian to feel that there are more advantages in close ties with Russia than with the EU. For example most of eastern Ukraine's trade is with Russia, Moscow pays very large sums of money for its Black Sea Fleet Crimean facilities, Russia provides gas well below global market prices, all of which would be at risk if links with Russia were significantly severed.
Furthermore as a BRIC nation Russia is widely seen as an emerging economic superpower. Today Russia has half the unemployment level that the EU has and twice the growth. Plus Europe is probably doomed to a long slow period of economic decline as the technological advantages it once had over underdeveloped world disappear due to modern easily transferred technologies - third world counties can now challenge Europe on the quality and quantity of manufactured goods.