Why Has SCOTUS Chief Roberts Abandoned Conservatism?

Why can't Republican presidents count on their Supreme Court picks to be reliably conservative? And, how was previously "conservative" Chief Judge John Roberts bamboozled into switching sides? Or did he just slump into compromise? Is Roberts proud of himself or merely insensate to his devolving circumstances? Maybe Roberts is the Caitlyn Jenner of SCOTUS, proving O'Sullivan's Law – that all institutions degenerate into liberalism except those founded as strictly conservative.  Recall, during Roberts' nomination he told the Senate he had no explicit judicial philosophy, adding: "It's my job to call balls and strikes, and not to pitch or bat." This is an existential view of judging. Roberts' main interest is preserving SCOTUS' reputation and power.