Questions like this are really just asking Zuckerberg to introduce his business in a controlled way.
Been a secret to "whom"? Not secret to technical people, no. There are plenty of non-technical people who still don't understand the "you are the product not a customer" trope. They see this free "talk to your family" service which sometimes shows ads which they ignore. They might answer the "how FB makes money question?" with "I don't know, maybe some people pay for it. Or maybe they are just nice and give it away for free".
Other questions might have been stupid but that particular one was typical of how a police investigator might start questioning or how a lawyer might cross examine a witness.
> I think most people will see the absolutely dismal lack of technical understanding by Congress
Back in the day I used to think of lawyers asking witness questions on the stand the same way: "Why do you ask him if he knows the victim, of course he does, these lawyers are sure not very bright..."
You really think most people have more technical understanding than these senators?
Also yes, based on their questions and age, I do think most people have a better understanding. Just the expressions of the other audience members and staff in the room shows the frustration.
This has never been secret and has been "on record" for a very long time. I think most people will see the absolutely dismal lack of technical understanding by Congress rather than any arrogance by Facebook as they too get fed up with these aimless questions.