This social lift collapsed with the USSR. After Yeltsin and his cronies replaced planned economy with laissez-faire capitalism, a fresh crop of oligarchs emerged by robbing and murdering their way through the nineties. The initial stage of accumulation of capital is never pretty, and the criminal situation in Russia back then can attest to that, but by 2000 the dust settled, Putin came and restored a semblance of order and the new aristocracy entrenched its positions.
the thing about this situation in 90s russia is that basically nothing like it has ever happened before, anywhere.
in 'normal' market economies, accumulation of capital was a process that happened slowly and gradually, over the course of many decades, sometimes centuries, with many large capital owners coming into their position by slowly growing an initially small business until it becomes very large, and their wealth grows along with it.
this is how the big industrialists of the 19th and 20th century came to dominate the economy in those times, and this is still how men like bezos, gates or musk came to dominate it today.
but soviet communism outlawed that process, for over half a century all economic activity was state owned and state controlled, business ownership did not exist, being an entrepreneur was illegal.
so when yeltsin decided he wanted a market eceonomy - well how do you get that when every person in the country has only ever known a communist command economy? who will run things, who will do business?
the idea of bringing in a bunch of foreign capitalists to take over and run shit was obviously not appealing to anybody, but no private person inside russia had any free market business experience either, nor any capital to get something started, so due to a lack of alternatives, things eventually just ended up falling into the hands of well connected members of the former soviet political and bureaucratic class, resulting in oligarchy to the extreme.
looking back, the idea that russia could simply skip past the slow, century long buildup that brought the capitalist states of the west to where they are today was pretty naive and obviously doomed to fail.
but on the other hand, i don't really see what yeltsin and his pals could have done differently to make things go smoother, he was in a pretty impossible situation all things considered.