text: I'll take  shot. CDF has a long and checkered history, but at least since the appointment of then-Cardinal Ratzinger (1981), has become less pastoral and more juridical-canonical. Pope Francis inherited as Prefect Cardinal Mueller, who has a pastoral side, but leans heavily toward the juridical-canonical work of the Congregation. By appointing Cardinal O'Malley, Pope Francis adds a pastoral voice that echoes throughout many parts of the Catholic world. In this sense, he appears to be sending a signal that he wants CDF to be more pastoral and that, if necessary, he will replace Mueller.
  Some commentators in Rome believe O'Malley is Francis' choice to succeed him, in which case a position in CDF would help make his case in a future conclave.