It’s been called the Autonomous Republic of Crimea since 1921. Ukraines had no association with Crimea until 1954, when Nikita Krushchev (himself a native of Ukraine) and premier of the Soviet Union transferred the Crimean Autonomous Soviet Socialist Republic from the Russian Federation to the Ukraine S.S.R. I guess the commies thought the U.S.S.R. was going to last forever. As far as I know, the Ukraines did nothing to deserve this prize and now the Russians, who wrested control of Crimea from the Ottoman Empire way back when, want it back. The Ukraine nationalists helped them by recently outlawing use of the Russian language, spoken by the majority of the Crimean population.
One correction, Khrushchev was ethnic Russian, he served as boss of Ukraine, under Stalin.
So he was trying to make nice with the Ukrainians, remember at the time he hadn’t fully consolidated power, so this was a gesture to get the Ukrainians on his side.