There are different sorts.
Tactical and strategic.
No one is suggesting that a few little green men appearing in Crimea would have resulted in a strategic strike on Moscow, but a few tactical nukes could have stopped Vlad's armour crossing into the east of Ukraine.
2 separate issues.
The reason for Vlad's invasion was because he didn't want the example of a kleptocrat being kicked out of office forming an example to the russian people that they could kick out their own crook in charge.
The giving up of the nukes didn't cause the invasion, they just were...
But that completely misses the central point that if Ukraine hadn't given up it's nukes in return for the ( worthless ) Budapest Memorandum, then the Crook in the Kremlin wouldn't have risked an invasion.