I don't trust either of them.
well that's a given...
but Russia still isn't suicidal. As much as they love twisting our tails for their profit, they don't want those maniacs with nukes anymore than we do.
It's a cyclic thing. They've made their money on Iran by selling their arms and all that (same with China) but now that Iran is able to bite back, they want to be on the side of the "Good Guys"