“Some demographers suggest that it reflects in the first instance the end of government subsidies to stimulate the birthrate; others point to the impact of the deepening socio-economic crisis in which Russia finds itself.”
Sounds a lot more plausible than foreign policy.
The only explanation that makes sense is Putin’s foreign policy caused the West to slap sanctions on Russia which caused or at least exacerbated the slumping economy in Russia. I suppose you could make a decent argument for that but the author never spelled that out. Sloppy writing.