Russia is currently fighting a war of aggression, applying controls on the flow of money in or out of there is one way in which the war machine can be starved.
"Aggression" is an objective measure. There is no subjectivity who starts a war and wo is in another country's territory. Those are observable facts.
And obviously Russia did not believe Ukraine to be a threat - or they would have not done this haphazard invasion with too little preparation and too few soldiers, so there is no excuse.
A state can always find a way to hide the transactions, on the other hand
I think the risk of sanctions, means that while there are work arounds, the cost of those work arounds, and the restrictions on who will do business with you, dramatically increase the costs of certain goods.
So sure, the cash moves, but now you pay more. A lot more. Death by 1000 cuts, and all that...
Russia is currently fighting a war of aggression, applying controls on the flow of money in or out of there is one way in which the war machine can be starved.