Just after the collapse of the World Trade Center in 2001, Leslie E. Robertson, the twin towers’ chief engineer, plunged into a period of moral reckoning.

As a young hotshot in the 1960s, Robertson had defied the engineering establishment to erect the iconic skyscrapers. Now, at age 73, he brooded. Over and over, observers suggested that the arrogant silhouette of the towers was their undoing. Robertson seemed surpassingly sad. He emailed a colleague in verse: “It is hard / But that I had done a bit more … / Had the towers stood up for just one minute longer … / It is hard.” As The Wall Street Journal reported, when asked at a public forum if he wished he had done anything differently, he wept.

But Robertson also conducted a careful audit of his work. The blueprints, the physics, the math came in for close review. He knew he had designed the buildings expressly to brook the impact of an airliner. But flaming jet fuel had brought them down. He concluded that inoculating the towers against those all-consuming fires would not have been feasible. “You could always prepare for more and more extreme events, but there has to be a risk analysis of what’s reasonable,” Robertson told a Newsweek reporter. In his reckoning, Robertson managed to avoid the twin seductions of defensiveness and ­self-savagery—and took responsibility for his work.

Mark Zuckerberg, an engineer in another key, has also seen his magnum opus breached, with a force that may yet shatter it. Over the past two and a half years, Facebook’s integrity as a place that “helps you connect and share with the people in your life” has been all but laid to waste—as it has served as a clearinghouse for propaganda, disinformation, fake news, and fraud accounts. More serious still: Facebook may not just have been vulnerable to information warfare; it may have been complicit.

Zuckerberg, however, has been unaccountably slow to make earnest amends. This week for Yom Kippur, 11 months after the election, he did post what’s known as a Cheshbon Hanefesh—the moral accounting undertaken annually in a spirit of repentance. But his statement seemed pro forma—perhaps even aggrieved. “For the ways my work was used to divide people rather than bring us together, I ask forgiveness and I will work to do better.” Odd phrasing. Was Zuckerberg confessing to his own misconduct? Or was he saying that his work “was used” by bad actors, which suggested that he himself was owed the amends?

But even this pass-agg penance marked a change of course for Zuckerberg personally, if not for Facebook. In November, fresh off the US election, he dismissed as “crazy” the idea that fake news on Facebook had influenced the race. (He disavowed the word when he came in for criticism 10 months later.) When President Obama reportedly urged Zuckerberg to take seriously that Facebook could be exploited by hostile powers intent on undermining democracy, even then Zuckerberg shrugged.

Meanwhile, he whistled in the dark, lighting off on a 50-state walkabout dense with Insta opportunities. It looked for all the world like he was running for president himself. That impression was bolstered when he later hired Joel Benenson, a former campaign adviser to Obama and ­Hillary Clinton.

As the summer wore on, it became unmistakable that Facebook’s problems ran deeper than fake news. In June, Facebook officials reportedly met with the Senate Intelligence Committee as part of that body’s investigation into Russia’s election interference. In August the BBC released an interview with a member of the Trump campaign saying, “Without Facebook we wouldn’t have won.”