The mask is off.

Sheryl Sandberg, once the human face of Facebook, the would-be feminist warrior whose “Lean In” philosophy was meant not just to reshape Big Tech but the American workplace and feminism itself, has been revealed as just another digital overlord.

The façade began crumbling last November, when The New York Times published a devastating exposé depicting Sandberg as the likely architect of an anti-Semitic smear campaign against George Soros in the wake of his attack on Facebook and Google at the 2018 World Economic Forum.

That story, of course, followed the revelations of rampant and promiscuous data sharing, the turgid response to ethnic cleansing in Myanmar — largely incited by false posts on the platform — and, of course, the company’s role in allowing Russian interference in the 2016 presidential election.

Yet Sandberg is still COO of Facebook. Why?

Once a media darling — the 2013 publication of her bestseller “Lean In” made her a mainstream star — Sandberg has been abandoned by the feminists who founded LeanIn.org as well as by outlets from The New York Times to The Atlantic to The Guardian, The Nation, the BBC, The Washington Post and Wired.

Even Michelle Obama dispatched with Sandberg’s facile, elitist premise — that women need to more strongly advocate for themselves at work, and corporations must do better by their female employees — with one succinct line.

“ ‘Lean in’ — that s–t doesn’t work all the time.”

Indeed. Especially if you lack the leverage of, say, a net worth estimated at $1.8 billion or a home with its own waterfall.

As Wired’s Virginia Heffernan noted in 2018, Facebook, with its 2.27 billion users, is an empire unto itself, governed by Sandberg and founder Mark Zuckerberg — autocrats who work in secret — hacking into the lives of users for purposes we are only beginning to understand, no rules to abide, no consequences to bear.

“She’s been reticent and even defensive when confronted about the extent of Facebook’s complicity in the rise of authoritarianism across the world,” Heffernan wrote. “She’s delayed in cleaning up the mess, stepping down or proposing serious reforms.”

That’s a polite way to put it.

As we go into 2020, the message we’re getting from Facebook is this: Wow, that actually happened. Don’t know if we can stop it from happening again. We probably can’t. In fact, next time is going to be worse, and the Russians are probably going to go after state and local elections. Deepfakes are beyond our control, too. Hey — it’s a global platform, and who among us doesn’t believe in free speech, right? Oh, and by the way, even though the world is catching on, we still plan to create our own global digital currency. Who’s going to stop us?

It’s been interesting to see Zuckerberg out front on that last one. Even though Congress asked both Zuckerberg and Sandberg to testify to their plans for Libra, only Zuckerberg sat before a House committee last month.

What does it mean when Sandberg — whose job description at least informally includes compensating for Zuckerberg’s dead-eyed, alien, lizard-blooded demeanor — sits this one out?

Perhaps Sandberg’s appearance the day before, at Vanity Fair’s New Establishment Summit in Beverly Hills, had something to do with it. Rather than parry softballs, interviewer Katie Couric went in hard and fast.

Why, Couric asked Sandberg, did Facebook declare, in September, that they would not fact-check political ads? “And I know you’re going to say, ‘We’re not a news organization,’ ” Couric said.

“We take political ads because we really believe they are part of the political discourse,” Sandberg said.

Really? Not propaganda, not electoral interference, not a threat to American democracy — but discourse?

Clearly, it’s been wish fulfillment to buy Sandberg as Facebook’s humanist component, the good mommy reining in a precociously gifted child who doesn’t yet understand his superpowers. As it turns out, she’s been raising Cain all along, at our great expense.