It isn’t really. Even Russia itself does not believe that the current rate is “real”. If it was Russia would have used its rubles to buy euros/dollars to pay its debt instead of defaulting by trying to pay with the rubble. Basically it is currently up artificially due to Russia buying rubbles with dollars/euros/gold/etc (and 20% interest rate) and them themselves pushing it the other way by trying to buy dollars/euros with rubbles would be counterproductive.

They are keeping it by burning through their foreign reserves.