Political Memes

It wasn't worth the paper it was written on from the start:

"Another key point was that U.S. State Department lawyers made a distinction between "security guarantee" and "security assurance", referring to the security guarantees that were desired by Ukraine in exchange for non-proliferation. "Security guarantee" would have implied the use of military force in assisting any non nuclear party (Ukraine, Belarus, Kazakhstan) being attacked by an aggressor (similar to Article 5 of the North Atlantic Treaty for NATO members) while "security assurance" would simply specify a promise of non-violation of these parties' territorial integrity. In the end, a statement was read into the negotiation record that the (according to the U.S. lawyers) lesser sense of the English word "assurance" would be the sole implied translation for all appearances of both terms in all three language versions of the statement."

https://en.m.wikipedia.org/wiki/Budapest_Memorandum

It has always read "I promise pinky promise swear I won't use military action against you but if anyone does I'm not obligated to come to your aid".

Ukraine signed it not because they misunderstood this, but because it wasn't their priority. They saw the nuclear weapons as a liability in themselves. They didn't have the skill or access to maintain or control them (Moscow had always retained operational control and the launch codes) and so they just wanted rid of them. They gave them up in exchange for massive energy deals, not a defence pact.