Where did you read this?
All it said was if Ukraine gives up its nuclear weapons, The US, Russia, and the UK would agree not to invade it. It never said if 1 of the three broke the agreement the other two would come to its defense.
Are you saying from the very beginning in 1994 Russia was already considered the evil militaristic neighbor of Ukraine which should be their top worry...not NATO? The entire Eastern block was duped for decades into thinking NATO was their biggest foe and with a snap of the fingers realized their biggest foe was actually lurking way behind their front lines...and immediately asked for protection from them?
Is this really your logic?