Cardinal Müller always seemed an odd fit for Francis, who elevated the German to become a prince of the church when he created his first batch of cardinals in February 2014.

As early as October 2013, with expectation rising in the church that Francis planned to open an avenue for divorced and remarried Catholics to receive communion, Cardinal Müller dampened the idea. In a long article published in L’Osservatore Romano, the church’s official paper, he wrote that the case for mercy “misses the mark.”

That pattern appeared again and again.

The pope proposed creating a tribunal to try bishops who mishandled sexual abuse cases, Cardinal Müller declared that the idea had “legal” difficulties, and the tribunal never came to be. Francis established a special commission to study the possibility of women as deacons, and Cardinal Müller flatly called the change “not possible.”

That dissonance between the pope’s inclusive messaging and Cardinal Müller’s door slamming intrigued Vatican watchers. Some Vatican analysts suggested that the cardinal played a useful role for Francis, perhaps as an ideological bad cop to his pastoral good cop, or as someone who provided political cover to protect the pontiff from conservative critics worried about the dissolution of the church’s orthodoxy.

But the powerful congregation, which Benedict, then Cardinal Joseph Ratzinger, led for years under John Paul II, seemed weakened, or even ignored, under Francis. The number of theologians or priests investigated for advocating supposedly suspect views shrank. And the congregation’s proposed corrections to Francis’ watershed document, Amoris Laetitia, or Joy of Love, before its publication last year were ignored.

It was that document that provided the most public division between Francis and Cardinal Müller, who made it clear that he viewed the most controversial aspects of the document through the prism of church tradition, and rejected the possibility that divorced Catholics who had remarried without an annulment could receive communion.

During the pope’s trip to Philadelphia in September 2015, Cardinal Müller said “it’s not possible” for violators of church doctrine on divorce, homosexuality or abortion to be welcomed completely back into the church. “It’s not an academic doctrine, it’s the word of God,” he said.