Donald Trump manages to be more sensible on Syria than Hilary

[Minimalist]

Putin is merely continuing a decades long Russian strategy of supporting the Assad family.  They have had access to a naval base in Syria since the 70's and it is their only such base in the Mediterranean.  Letting Assad fall risks losing that base as well as 40 years of Russian/Soviet influence.  Cynical?  Yes.  But nations have interests.