Through Budapest Memorandum on Security Assurances, Belarus, Kazakhstan and Ukraine gave up their nuclear weapons between 1994 and 1996. According to the same source:
Before that, Ukraine had the world's third largest nuclear weapons stockpile, of which Ukraine had physical if not operational control.
The signatories offered Ukraine "security assurances" in exchange for its adherence to the Treaty on the Non-Proliferation of Nuclear Weapons.
According to this article, this decision was not a wise one:
"As soon as it declared independence, Ukraine should have been quietly encouraged to fashion its own nuclear deterrent," the University of Chicago scholar wrote in a 1993 Foreign Policy piece. "A nuclear Ukraine ... is imperative to maintain peace between Ukraine and Russia. ... Ukraine cannot defend itself against a nuclear-armed Russia with conventional weapons, and no state, including the United States, is going to extend to it a meaningful security guarantee."
Question: why did Ukraine apparently give up the nuclear weapons so easily? What did it gain to counterbalance giving up to such a strategic advantage?