Ukraine never owned nukes. The Soviet Union owned and controlled those nukes.
After the Soviet breakup, the participants had to decide who got custody of what, as in any divorce. Russia got the USSR's seat on the UN Security Council. Russia also got all the nukes.
Did Ukraine have a choice? Soviet soldiers (many -- most? --- of them Russian) manned the nukes that were stationed in Ukraine. Essentially, the Russians took home what was theirs.
i think it’s not quite that black and white. they were a bargaining chip for the Ukrainians - which is why they demanded Budapest Agreement. there continues to be regret over the agreement - even from Clinton himself.https://nypost.com/2023/04/05/bill-clinton-regrets-having-ukraine-give-up-nuclear-weapons/ so i suspect the Soviets didn’t consider they had 100% control, no matter who owned them. location location location.