You seem to be implying that there is some sort of rule that there should only be one Russian driver in F1. Why shouldn't Russian sponsors only support one (or several) particular drivers, just like sponsors from elsewhere do? Do you think that Ericcson's sponsors would pull out if Rosenqvist got a F1 seat because they only need to have one Swede in F1?
I never said there is a rule. There is only what was reported last december. SMP's owner who is a close friend of the 'top' was asked by that same "top" to do what is necessary to have a Russian driver in F1 as there was none to go with Sochi. The occasion had arisen with Williams and they went for it pretty aggressively and quickly offered Williamd something they could not refuse. Kubica himself said the day before the driver was announced he was 99.9% sure he was to be. The Russians achieved their goal.
They are not stupid, to pay so much for a mediocre driver when they have other candidates like Markelov? it's pretty obvious they will look to get better return for their money. Second, if there is 1 or 2 other Russians already in F1 (could be Mazepin and Kvyat), is there a need anymore to pay at all ? The incentive loses its strength (and money offer) with every Russian already in.
Someone for some reason would want to have fun in world of F1 and buys a team. Unless the "top" decides to be more involved and have a full team with 2 Russian drivers, Sirotkin may be on the way out soon. Anyways there's only 1 way is to see Williams follow Force India and declare bankruptcy.
Tbh I'm surprised how sure Sirotkin is about staying in F1...he may get lucky and get another season, but that could be it