We know that, most of the world knows that, the Chinese know even.Russia litterally didn't have the logistical power or reach to hold onto it if it was even remotely contested. Also Russia is the largest country on the planet, they more or less have all of the resources they need inside their territory and they cant even fully exploit that.
However the brainwashing out of Moscow is not something that can be discounnted from making colossally retarded ideas viable for the Russian public.