The appearance by Hillary Clinton before Trey Gowdy' committee shared some lessons she probably paid a lot of money to learn, and those lessons came free of charge to the rest of us. They could be useful for anyone who is ever a party to a criminal or civil trial.
The lesson was for the witness to stay calm, don't get angry, and most importantly, answer with confidence that what you are saying is the truth. Don't react to negative information, simply act as if that's what you expected. Anyone watching might be led to think everything you did was perfectly normal.
Listening to some of the talking heads after the hearing suggests that that's all that matters to the observers. The facts didn't matter so much. What scored the points were the witness' attitude, demeanor, appearance and body language.
Now the pundits are ready to usher Clinton into the white house.