I am sure this is not because Russian oligarchy is trying to move all the stolen money back into Russia because of fear it being confiscated in the west.
I don't understand the latter. What's the point of doing that? It's a very great deal of money, so there should be some really good reason.
[1] https://www.nytimes.com/2022/04/01/opinion/russia-ruble-econ... [2] https://www.nytimes.com/2022/05/09/business/elvira-nabiullin...
The central bank of Russia has just relaxed its controls on Russians moving money to friendly countries.
https://apple.news/AfMMfcmbfTHS_nbGj96-nRA
Isn’t it just the case that Russians have no need of dollars because they can’t buy anything with them. So they get rid of them for roubles which they can use to buy things.
Demand and supply does the rest.
I assume the sanctions also cover Indian subsidiaries, so the Russians won't be able to trade against e.g. Goldman Sachs's Indian subsidiary. But there are plenty of banks that aren't owned by motherships in the two dozen sanctioning countries.
They were probably outright selling lots of currency during the hot days in Feb and March to stop the immediate exchange rate freefall, that's where the $50B most likely went. Since then, the imports plummeted but the export dollar amounts soared because of high energy prices (despite slightly lower physical volumes), so the curbs and the market took over for now. We'll see what happens next.
Btw: no, selling rubles is not forbidden, as a consumer you could sell rubles pretty close to official exchange rate in April (not sure about now), and they just announced you can wire $50k to foreign banks per month starting today. No idea about larger amounts.