It's even worse than that. The ruling elite knows that on the one hand it's non-removable, but on the other its days are numbered (Putin is quite old and he won

It's even worse than that. The ruling elite knows that on the one hand it's non-removable, but on the other its days are numbered (Putin is quite old and he won't live forever; what happens after he dies is anybody's guess), so they pillage and burn whatever they can while they can, with impunity. Diversifying the economy would require a long term view. The folks currently in power don't even realize anything is wrong per se - oil and gas money works pretty well for them.