FX market rates in medium and short term are a result of flows, in simple terms supply and demand. Longer term fundamentals should work (ie different in real rates, inflation, balance of payments) but they really don't.
So FX rate can be floating, pegged or target a certain band. Rouble was free floating with market demand and supply doing the heavy lifting for the price discovery. Even though Russia is a next exporter (which in theory should lead to appreciating stronger currency) its currency was undervalued according to PPP metric by about 2/3 of its value.
Come in effect sanctions that freeze Russia's central banks foreign reserves (accumulated USD,EUR and other basket of currencies invested in various fixed income assets across the world) as well as introducing swift bans and other measures that in effect. That causes a huge capital flight out of the country, everybody who can rushes to convert their roubles into other currencies. Demand for rouble is zero. Central bank has its reserves frozen and cannot use it to stabilise the FX rate. Rouble starts collapsing.
Russian government and central bank enact certain laws and rules so as to prevent the capital flight. 80% of foreign currency income has to be converted into rouble. Citizen cannot convert more than $10k USD (flat number, not per month or year) until a certain date ( I don't remember which).
A lot of people online seem to resort to copium that rouble appreciation is artificial but in reality rouble depreciation was also artificial. There's an economic war going on.
As Russia has introduced capital controls it has all the ability to set up any rouble rate it wants, it is not longer a function of a free market price discovery.
Once again, a lot of people not familiar with economics are looking to see the effect of the economic war on the exchange rate but it is not productive. If you want to see sanctions damage then look at GDP forecast growth. At the moment it is expected that the Russia economy will contract by 10% but the situation is very fluid and may change dramatically demanding how things will unfold and whether more heavy sanctions and or oil embargo will hit. (in case of historical analysis I do not remember figures exactly but roughly it was estimated that 2014 sanctions against Russia caused about 1.5-2.5% of GDP loss per year for Russia).
