I can see two reasons why one or more of the conservative justices might have voted against reviewing the state SSM cases. If you are certain or nearly certain that Justice Kennedy will go south, denying review (1) minimizes the near-term damage and leaves open the slender possibility that a Court with slightly altered membership might in the not-so-distant future refrain from inventing a national SSM right, and (2) prevents Justice Kennedy from issuing another insufferable opinion replete with “mystery of human life” blather. I’d give more weight to the second than the first.
I’m inclined to think that the lack of a public dissent signals a real fatigue and resignation among the conservative justices.