Cardinal George Pell walks to a car in Melbourne on Dec. 11. He was convicted of “historical” child sexual offences. (William West/AFP/Getty Images)

CARDINAL GEORGE PELL was, as Vatican treasurer, one of the Catholic Church’s most powerful figures and a senior counselor to Pope Francis, until Mr. Pell was placed on a leave of absence last year. Last week, he was convicted in an Australian court on what were referred to there as “historical” sex abuse charges. That locution seemed to diminish the events themselves, which, as a unanimous jury found, occurred decades ago. Yet the crucible of clergy sex abuse remains a thoroughly contemporary blight for the church, for the Vatican and for Francis, whose papacy, already blemished by his flailing and shuffling on the issue, hangs in the balance.

Long-standing accusations related to the mishandling and coverup of clergy sex offenses have dogged Mr. Pell for years, and were lodged formally two years ago before a Royal Commission in Australia investigating the scandals and the church’s complicity. Last year, Mr. Pell was charged with abuse himself in a case involving two choir boys stemming from the 1990s, when he was archbishop of Melbourne, according to the Daily Beast, which first reported last week’s verdict. Mr. Pell has denied the allegations.

It was only after the formal charges were brought last year that Mr. Pell, often described as the Vatican’s No. 3 official, was placed on leave to return to his native Australia to defend himself. And it was only last week, just after the court in Melbourne rendered its verdict, that the Vatican announced that he had been removed, in October, well after the trial was underway, from a top papal advisory body known as the Council of Cardinals.

That response typifies the pope’s foot-dragging and half-measures in the face of allegations that date back years or decades. In Mr. Pell’s case, it had been known for years, well before he was elevated to lead the Holy See’s finances in 2014, that as a young priest he had been aware of the abuse of dozens of children by other priests in his hometown of Ballarat. The events in Ballarat were notorious in Australia; from one fourth-grade class of 33 boys, 12 died by suicide, The Post reported in 2015 — yet somehow they did not set off alarm bells in the Vatican’s lofty confines. Even now, Mr. Pell remains a cardinal.

The pope has summoned the leaders of the world’s conferences of bishops to the Vatican in February for what church leaders suggest will be a reckoning with a scandal that burst into global view nearly 17 years ago. The conclave was impelled not so much by newly enlightened thinking in Rome as by the fallout after a Pennsylvania grand jury’s report, in the summer, that found more than 300 priests had abused more than 1,000 children over the course of decades.

In fact, the scale of the church’s complicity was clear previously, from revelations heaped upon revelations. The conviction of Mr. Pell, though he is the highest-ranking church official so implicated, is simply the latest, among countless pieces of evidence, that argue for broad, deep and painful reforms — precisely the sort of overhaul that the pope has so far resisted.