The focus of this article is about how unprecedented it is for Iran to let Russia, or anyone else, base military forces in their territory. But I think just as interesting is the fact that when Russian and Iranian interests converge, the two countries are able to find ways to cooperate with each other to achieve their common goals. U.S. and Iranian interests have converged several times in the past two decades (most notably just after 9/11, and when the U.S. was propping up the Shiite government of Iraq), but the two countries just can't get past their contentious history to work constructively together even in situations when Iran and the U.S. are on the exact same side.
Russia and Iran have had a contentious history too! But that was a lot further in the past. So I guess there's hope that some day, a century or two from now, Iran and the U.S. will be able to cooperate when their interests coincide.