To be fair to Congress, their job is really to shape events in the public interest. Considering these hearings to be pure fact-finding is a category error. If they browbeat a celebrity, this shapes events in multiple ways: it affects fundraising, it affects the behavior of the individual browbeaten and those in this individual's orbit, it affects the public narrative, and if affects actions at the voting booth. And that is only the beginning. It is an extremely complicated game with numerous players and feedback loops. You can call it "grandstanding", as though it's purposeless and ineffectual, but obviously it isn't, and really this is their job. They want to speak to certain people because they calculate that this will give them leverage to shape events in a certain way.

This is how the sausage is made.