For what it’s worth, here’s my theory explaining yesterday’s order denying review in the SSM cases:
One or more of the three conservative justices who might most be expected to object to denial—that is, Scalia, Thomas, or Alito—instead concluded that denial was the best course. Why? Because that justice (or those justices) became convinced that Kennedy was beyond persuasion and that he was a certain fifth vote to invent a constitutional right to same-sex marriage. On that understanding, the least-worst option would be to deny review and thus (for the time being, at least) prevent the Supreme Court from placing its formal imprimatur on the developments below.
I think that this is the only theory that adequately explains why none of these three justices publicly registered a dissent. In particular, I don’t think that a competing theory—that the Chief Justice voted to deny but that Scalia, Thomas, and Alito all voted to grant—can explain the absence of a public dissent.
I don’t think that there’s any difficulty explaining why the four liberals would go along with the denial. Even if they’re equally confident of Kennedy, it’s much easier from their perspective to let the lower courts do the spadework and to intervene only if and when a court rules against a constitutional SSM right.