Congress members prepare ahead of time
When members of Congress are part of a hearing like this one, they're not going to be coming up with their questions on the spot. They will have prepared extensively in order to make sure that they ask all the questions they need in order to get the information (or make all the statements) they want.
In theory they could adjust the questions that they are going to ask based on which questions other members have already asked, but the more you alter a prepared plan the more likely it is that you'll make mistakes when trying to implement that plan. Asking a question multiple times is far preferable to skipping a question because you mistakenly thought that it had already been asked, or because you were removing other questions and it got mixed in.
So they stick with what's safe, and ask their questions even if those questions have already been asked during the hearing.