Russia's position on this has been rather clear for a while.
It does not recognize the territory that Armenia took from Azerbaijan as legitimate. Therefore, it is not required or interested to defend said territory. They will however, keep Azerbaijan from trying to press any attacks into Armenia proper. Azerbaijan has an edge in this in that Turkey recognizes its right to retake the lost territory.
And Russia snickering because if I recall, they were the ones who drew the lines where lots of Armenians would be living in Azerbaijan from the get go. This is really just a part of Russia's divide and rule strategy.