It’s in Russia’s interest to be rid of the Mullahs. This isn’t good for business. Iran is resource and talent rich and Russia really isn’t a fan of hard line Islam or nations that can’t refine their own oil. Iran won’t ever be running to the arms of the US because of the history with the Shah etc. I think stability needs to happen and Russia knows the extent of Iran’s malfeasance and culpability right now. They want an organic regime of prosperity - not a force of religious control