Ukraine also probably had half the engineers and scientists that built the damn things in the first place considering how much of the Soviet nuclear industry was located in Ukraine at the time.

They ended up with the 3rd largest nuclear stockpile and whilst they would probably would get invaded by both sides if they didn’t surrender the nukes and attempted to assert operational control over them they surely had that capability.

Also back then the primary fear was that some of those nukes would end up on the open market, Iran, Iraq, Pakistan, Libya, North Korea heck even South Africa back then were all likely buyers.