[throw-the-towel]

To be fair, Russia becoming the single successor of the USSR wasn't a foregone conclusion in the early 1990s. There wasn't relevant precedent of a country dissolving I think -- Yugoslavia was still battling it out, Austria-Hungary was too long ago.

[int_19h]

It was an explicit decision by both CIS and UN. Russia took USSR's seat on UNSC two weeks after USSR was dissolved, and that happened in 1991. Budapest Memorandum was negotiated 3 years later, by which time this was already a firmly established thing.