"Wound up" has (at least) two other meanings.
It can be used to described tightening a spring that powers some mechanical device. Like, "He wound up his watch."
It can also mean "prepared". I think this meaning comes from the previous meaning and from baseball. We say, "The pitcher wound up and threw the ball", meaning he swung his arm around in a circle a few times, like you turn a knob or key in a circle to wind up a watch, and then he threw the ball. So we use it metaphorically to mean "prepared". Like, "George wound up and delivered his speech."
I think the meaning here is like that last meaning. The senators "wound up", i.e. prepared, like a baseball player preparing to throw a ball, comments that they "threw" at the witness.
Understand that when members of congress ask questions of a witness during a hearing, the purpose is often not to gain information from the witness. Sometimes a person knowledgeable about some subject will appear before Congress and they'll ask questions to learn from this person. But often it's all a political exercise. The purpose of the question is to give the witness an opportunity to make some political point that the congressman wants to make, or to force them to admit something that the congressman wants to drag out of them. In the case of a nominee for some important position, congressmen who support the nominee will ask softball questions to invite the nominee to recite their qualifications, like, "Mr Nominee, please tell us about when you received the Nobel Prize." Congressmen who oppose the nominee will ask "gotcha" questions, like, "Isn't it true that in 2004 you were convicted of drunk driving?", or "What is your position on controversial question X?"
