the reason they gave up their nuclear weapons was that it was an expensive and cumbersome responsibility that they had no practical use for outside of dirty bombs and terrorist tactics, as they didnt have the means to launch the missiles.
an often forgotten bit of information too, is that during this time, the USA was NOT friendly with Ukraine, the US Government did not Trust Ukraine an inch, and was not going to tolerate them to have nuclear weapons.
in 1991 the world went from having like 7 Nuclear states, to 10 all in the blink of an eye. and the 7 who were there before, wanted the new crowd removed immediatley from the club
The world treated the Russian Federation as if it was the replacement for the USSR, and Ukraine, Belarus and Kazakhstan were not going to be tolerated keeping these weapons, if they did, they would have been treated like North Korea or Iran.
NATO will not see any new members again.
the Alliance is more or less defunct as there are trojan horses in it like Hungary, and America's refusal to honor Article 5 is an open secret now.