I just explained it to you and you ignored my comment. Here is a simplification if it helps:
1991-1994: They nuke Moscow.
1994-present day: American strategic deterrence takes over.
If any part of that is unclear to you then I urge that you reread the Budapest Memorandum on Security Assurances and return to the discussion with the rest of the context.
Anduril does not manufacture strategic deterrents. If you think they're the solution to the Budapest Memorandum then you're the sort of armchair YouTube General that the Army filters out in officer school. It's not hard to understand, anyone can Google the difference between strategy and tactics.
Ukraine keeping the nukes was never going to happen. The US, EU, and Russia were all in agreement on that. Ukraine was in shambles at the time, and no one wanted the risk of nukes getting transferred or sold outside of the existing nuclear club.
Ukraine had physical possession of the nukes, but their ability to actually use them was highly suspect. They might have been able to circumvent the security measures given enough time, but if anything such an attempt would have sparked an international "peacekeeping operation" to make sure the nukes didn't fall into the wrong hands.
Well, for all the wanting of nonproliferation it didn't stop Pakistan or India. I never saw any peacekeeping operations from China or Russia when either of them went nuclear.
If Ukraine had the physics package, why couldn't they deploy it? Barring launch codes from the Kremlin, there's still enriched uranium in the warhead that you can turn into a simpler one-stage bomb. I doubt they could have gone thermonuclear, but simply leveraging the ICBMs and fissile material seems well within Ukraine's wheelhouse.
