Congressional testimony is negotiated ahead of time. Questions and answers are negotiated, with little straying from the script allowed. That’s why everyone involved is reading or looking bored, and why obvious follow up questions don’t happen.
Doubt that? Contact a Congressman’s office and ask.
I was hopeful about “Swamp drain”. It turned out to be a campaign talking point that never came to fruition. I don’t think we will ever see that purge unless it is done correctly and that is rather messy.