Congressional inquiries are nothing more than the ability for legislators to showboat their "power" to make things change. They capitalize on citizen concern regarding an issue, call the accused parties to testify and...then what?
They saw the opportunity to haul Mark Zuckerberg in front of the panel because people were concerned about data privacy. They asked a bunch of fairly unsophisticated questions...and, the result?
Nothing...other than Zuckerberg made an estimated $3 billion as his stock increased on Congress' inane inquisition.