How did the oligarchs benefit from the fall of the Soviet Union?

Russian oligarchs are business oligarchs of the former Soviet republics who rapidly accumulated wealth during the era of Russian privatization in the aftermath of the dissolution of the Soviet Union in the 1990s. The failing Soviet state left the ownership of state assets contested, which allowed for informal deals with former USSR officials (mostly in Russia and Ukraine) as a means to acquire state property. Historian Edward L. Keenan has drawn a comparison between the current Russian phenomenon of oligarchs and the system of powerful boyars which emerged in late-Medieval Muscovy