The idea is that if they do this, then they could make sure that they sell that bitcoin for ruble and gather all the ruble all around the world. Not just inside their nation, but get bitcoin from others, and this would earn them a ton of bitcoin, then sell it and get dollars, or euros, and then they could sell those and get ruble.
What this does is put a lot more dollars into the world since they are selling it, and taking more ruble out of the circulation because they are buying it. As we can see, that would work. However, they are already doing fine to be fair and I do not think that they would need something like that at this point.
With decentralized exchanges and P2P trading platforms, it may be possible to trade BTC for Ruble or vice versa even with economic sanctions in play. But Russia still has some allies willing to purchase its petroleum and natural gas reserves, so legalizing Bitcoin would not be a priority right now. Even if Bitcoin never gets the approval of Russia, government officials can still use it "behind the scenes". It's a decentralized and open source cryptocurrency after all.
Adoption for BTC is growing worldwide, so it should only be a matter of time before "hyperbitcoinization" becomes a reality. Just my opinion

like China, India, they are allies of Russia who are willing to buy oil and gas from Russia, so the sanctions imposed on Russia do not seem to be a significant obstacle, on the other hand Russia sends vaccines to North Korea which means that they also have good relations, So in this case Russia is not alone, especially for western countries, oil and gas from Russia are the dominant supply for them, so that by imposing sanctions, they will certainly find themselves in trouble.
True, Russia has close economic relationships with nations like China and India, and these ties can lessen the effects of sanctions. Additionally, Russia has considerable negotiating power in the face of impending sanctions thanks to its capacity to export gas and oil to Western nations.