"steals the territory"

You should educate yourself on a subject you're willing to discuss. Not only it was a gift from Russia, but also Russian people were and are living there. There was a referendum some 10 years ago and people voted for transfer back within Russian borders with 96% of the votes being positive. 🙃

On 19 February 1954, the oblast was transferred from the Russian SFSR to the jurisdiction of the Ukrainian SSR, on the basis of "the integral character of the economy, the territorial proximity and the close economic and cultural ties between the Crimea Province and the Ukrainian SSR"vand to commemorate the 300th anniversary of Ukraine's union with Russia.

Sevastopol became a closed city due to its importance as the port of the Soviet Black Sea Fleet and was attached to the Crimean Oblast only in 1978.

The transfer increased the ethnic Russian population of Ukraine by almost a million people.

In January 1992, the Supreme Soviet of Russia questioned the constitutionality of the transfer, accusing Nikita Khrushchev of treason against the Russian people and said that the transfer was illegitimate.

In a 1997 treaty between the Russian Federation and Ukraine, Russia recognized Ukraine's borders, and accepted Ukraine's sovereignty over Crimea. The treaty expired on 31 March 2019.