"Crimea," said Potemkin, "is the wart on Russia's nose". It wasn't always. For five hundred years it was ruled by Muslims, descendants of the Mongol horde, but most of them left in the three-quarters of a century between Catherine the Great's destructive policy of Russification and the end of the Crimean War. Stalin saw to the rest, deporting the Tatar population en masse on the trumped-up charge of collaboration with the Nazis. They weren't allowed back until 1989 and now make up just 12% of the near two million inhabitants.
To the majority Russian population Crimea has always been theirs. Or at least it was never Ukraine's. When Krushchev transferred the peninsula from Russia to the Ukrainian Soviet Socialist Republic in 1954 most of his countrymen thought he must have been drunk. In 1991 88% of Crimeans voted against the dissolution of the Soviet Union, two-thirds of the population speak Russian as their first language, and Russia's Black Sea Fleet still has its base in the city of Sevastopol.
None of which is likely to change anytime soon.