Russia has 140 million people, the world's 11th economy, and, despite the impression one might have watching the news, only US/Europe (plus usual dependencies in Asia) have imposed sanctions on them. That is to say, there is still a lot of trade between Russia and the outside world (and the central bank does not seem to be printing money like mad).
Edit: It looks like the 50% drop only last a day. The rubble has since steadily somewhat recovered to 'only' about a 30% drop, which may also be due to Russian government intervention.
Russia does have some structural disadvantages compared with the Netherlands (e.g. it is stretched out over a whole lot of extremely cold territory and it has a crumbling soviet infrastructure in places where it should not) but is in the position that it is in quite a large part due to corruptly exfiltrated wealth over almost two generations.
Money that should have gone to fixing that infrastructure has instead disappeared out of the country, starting in smaller ways through the more western-friendly comecon states and then accelerating with every market reform.
That money now creates wealth entirely in the West and has done for thirty years.
Edit: It looks like the 50% drop only last a day. The rubble has since steadily somewhat recovered to 'only' about a 30% drop, which may also be due to Russian government intervention.