He attributed that in part to the format for Tuesday's joint hearing before the Senate's Commerce and Judiciary committees that will give Zuckerberg an advantage, saying it would favour spectacle over thoughtful dialogue.
Cambridge Analytica's, third-party quiz app, This Is Your Digitial Life, is at the center of the breach. "And our goals are to understand Facebook's impact on upcoming elections - like Brazil, India, Mexico and the United States midterms - and to inform our future product and policy decisions", Facebook said in a statement.
That's one of many questions Congress should demand that Zuckerberg answer. "We didn't take a broad enough view of our responsibility, and that was a big mistake", Zuckerberg plans to say.
"This was kind of an app that was being promoted during and around the election, and basically you could download this app, and then you could take this survey about different things, and then they would actually pay you", Epicosity Social Media Coordinator Skyler Crabill said. "An American company, I believe, has a responsibility to America".
Mark R. Warner, the ranking Democrat on the Senate Select Committee on Intelligence, told WVTF Virginia Public Radio recently.
Zuckerberg also addresses the 2016 election, explaining the website's efforts to block "traditional threats" like hacking and malware, and the company's failure to identify or prevent disinformation campaigns and the coordinated use of fake accounts. Moreover, Facebook says it will not have approval over the research topics or findings.
Zuckerberg's testimony said the company was "too slow to spot and respond to Russian interference, and we're working hard to get better".
Mark Zuckerberg attended meetings on Capitol Hill on Monday.
Congress will likely make the point that Facebook is a company, not a philanthropy, and has made decisions based on incentives that don't align with helping users, especially with regards to privacy.
You know how before you access a game (or any other application) in Facebook, it asks permission to also access a bunch of your information?
For hearings a year ago about Russia's alleged use of social media to influence American politics, Facebook, Twitter Inc and Alphabet Inc's Google sent lawyers, angering lawmakers.
Approximately 87 million of Facebook's account holders may have had their personal information shared, according to the social media company.
Zuckerberg has been unclear about whether Facebook would extend the European protections to the USA and elsewhere. At a minimum, it will have achieved something if it gets Facebook to give up the saccharine one-world rhetoric about its mission and admit the bottom line is as important to it as any other profit-making company.
He's expected to concede that Facebook "didn't do enough" to prevent a host of problems on its platform, such as fake news, foreign interference in elections, hate speech and data privacy. Nelson said it would be "very difficult" to impose regulations, particularly during the current administration. If it's the latter, why shouldn't Facebook allow people to opt out of being targeted by ads?
"People have this idea that we are going to pass omnibus privacy legislation and it is going to be a silver bullet", said Alvaro Bedoya, a former congressional aide who worked on privacy issues for former Senator Al Franken.
Facebook's previous emissary "was a silver-tongued devil" who "said nothing", Republican Senator John Kennedy said on CNBC on Monday.