You seem to be labouring under the same misapprehension that afflicts many in the West.

The nukes that were in Ukraine were never "Ukrainian" - any more than the nukes stationed in Germany belong to the Germans.

The nuclear weapons that were placed in Ukraine belonged to the Soviet Union. The targeting, launch control, etc. was all controlled in Moscow. The Ukrainians never could have used them even if they wanted to. Certainly the Russians had the ability to disable or sabotage them at any time.

After the fall of the USSR, the nukes in Ukraine needed to be decommissioned because they served no purpose other than to provide a tempting, juicy target for international terrorists.

There was also the very real danger that the staggeringly corrupt Ukrainians would sell them on the black market.