Memes

The Budapest Memorandum was explicitly stated to not be legally binding. It wasn't guarantees, but assurances, and the US broke these assurances first:

“Although the Memorandum is not legally binding, we take these political commitments seriously and do not believe any U.S. sanctions, whether imposed because of human rights or non-proliferation concerns, are inconsistent with our commitments to Belarus under the Memorandum or undermine them. Rather, sanctions are aimed at securing the human rights of Belarusians and combating the proliferation of weapons of mass destruction and other illicit activities, not at gaining any advantage for the United States”.

This was the reasoning given for sanctioning Belarus in 2013. The west backing the far-right Banderite coup in 2014 was an even greater violation of Ukrainian sovereignty. Ukraine also did not give up "its" nukes, but returned the soviet nukes Moscow had stationed there prior to the dissolution of the USSR that were a part of the multi-national nature of the soviet union.

The Budapest Memorandum was neither binding nor respected by the west to begin with.