USSR dissolved in 1991 when its last member state, Khazakstan, left. Russia, which had left the union prior, found itself with a lot of nuclear warheads. Other ex-member states agreed to hand the nukes they had to Russia. Having nuclear weapons and having the means to maintain them and launch them, Russia naturally joined the Security Council in 1991.

It’s kind of a revolution though because it all started with Maydan and the ousting of Russian puppet Yanukovitch.