There are a few things here:
The Defense of Marriage Act decision overshadowed another 2013 case―Hollingsworth v. Perry―that could have determined whether states could ban same-sex marriage.
The case concerned a challenge to California’s Proposition 8, a state constitutional amendment that barred same-sex couples from marriage. But Roberts, writing for the majority, dismissed the case, holding that the challengers did not have the legal standing to bring it to the court.
The ruling left in place a lower court decision that had invalidated Proposition 8 and thus paved the way for same-sex marriage in California. Roberts’ lesbian cousin, who lives in California, sat in the courtroom during arguments in the Prop 8 case.
Few people predicted that the issue would return so quickly to the Supreme Court, but waves of lower court judges―sometimes citing Windsor―struck down the state bans.
Ariane de Vogue is not wrong. It seemed strange at the time; the Hollingsworth outcome was one of my anti-prophet moments. When the case was selected, I actually told a friend it wouldn’t make sense for the Court to take the case and then punt. And, yet, here we are.