They have the biggest gas reserves of any nation. Everybody buys Russian gas but now that Russia is threatening to shut down gas delivery all their customers are moving away from gas and onto other resources.
So the one thing that made Russia(n oligarchs) wealthy will soon be obsolete. Russia might be the largest nation in the world but
about 87% of it is barren land, uninhabitable and unfarmable. They ofcourse have other resources in their lands which we buy or need, but none are so important as their gas. And that is the one thing we are now getting rid of in an heavily accelerated timeline.
Hypothetically speaking Russia could try to use its own resources to make up the losses. They could attempt to make their own McBurger or MotherLand Rover but they will likely not succeed. There is precedent here and we do not have to look too far back into their history to know that they cant cut it on their own. The USSR was not a great place. And now that they have grown accustomed to western/capitalist luxuries it will be tough going back to the old ways.