Russia always said that their interest was to de-militarize Ukraine, and that they are doing better than even they probably thought possible.  Territorial/economic gains would seem to be an unanticipated windfall.  They have more of an ethical obligation than a simple opportunity take it as such, and the people living in the areas they appropriate will be the lucky ones if the last 20 or so years is anything to go by.  The citizens voted overwhelmingly to do that  in the areas where they had an opportunity to do so.