You're assuming that the questions are asked solely for the public record.
Here's another reason...
Members of Congress want video of themselves asking good questions that will be broadcast by their local news media and / or used in campaign commercials.
And another... Often times you'll notice that committee seats are empty during hearings.
That's because members come and go during the hearing.
It's possible that one member asks a question that was asked by another member earlier in the day before the first member arrived.
(Although I don't think that was the case in the Cohen hearing, as the entire committee seemed to be present for the duration.)
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Members of Congress may not fully trust the witness.
This is especially the case with Michael Cohen, who has been convicted of lying to Congress.
Asking a witness about the same thing multiple times makes them more likely to contradict themselves (or their written testimony) if they're lying.
Witnesses sometimes dodge questions or give incomplete answers.
Members that aren't satisfied may ask again to press for more information.
Rep. Clay Higgins (R-LA) specifically gave this as a reason for one of his questions during Cohen's recent hearing .
I'm going to give you another opportunity to respond what you brushed off earlier regarding your own statement during this testimony...
Grandstanding.
The members may be looking to create clips and soundbites of themselves that can be politically beneficial in the future.
On the flip side, when the witness is themselves a politician, opponents who sit on the committee can use the hearing as an opportunity to politically damage the witness.
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In the example you cite, it was an extremely important question that links the president directly to a felony.
If you have been asked this multiple times, it reinforces the answer and makes it impossible for you to walk back your answer later.
Normally prosecutors ask the same question multiple time you are looking for any inconsistencies in the answer.
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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.
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Public Congressional hearings are nothing but spectacles for voters masked as a serious inquiry.
Nothing ever comes out of them besides hours of video footage, as Congressmen don't need these hearings to arrive to any important decisions.
At best, these hearings serve to justify a proposed law that's already been decided upon by one of the parties.
At worst it's just a waste of taxpayer money and a way for individual Congressmen to show off how tough and inquisitive they are.
In this context it becomes clear that Congressmen only ask questions which make them look good on TV.
And if one Congressmen finds a question that sounds good to the average Joe in their state, there's a high chance others would copycat them.
It could also be explained by laziness - since Congressmen don't really care about what's being said at the hearing, they're likewise too lazy to bother to follow what's been asked before.
Sure, a few people would laugh at their supposed ignorance, but most voters won't notice that something's amiss.
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I must've seen at least 3 Congressmen ask Michael Cohen, President Trump's former personal attorney, who Individual 1 was, despite the fact that in the beginning he had already said it was Donald Trump, and despite the fact that previous members had already asked him that question, as well.  What is the reason for this? What benefit does it have when the statement is already in the record?
Why do members of Congress in committee hearings ask witnesses the same question multiple times?
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Members of Congress want video of themselves asking good questions that will be broadcast by their local news media and / or used in campaign commercials. In this      context it becomes clear that Congressmen only ask questions which make them look good on TV - this can also be used to create clips and soundbites that can be politically beneficial in the future.  Asking a witness about the same thing multiple times makes them more likely to contradict themselves if they're lying.  Members that aren't satisfied may then ask again to press for more information. Congress members  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. Members of congress want their questions broadcast for public support. Also, witnesses are more likely to contradict themselves by being asked the same question more than once if they are telling lies and thus this method reinforces their answer.
Members of congress want their questions broadcast for public support. Witnesses are more likely to contradict themselves by being asked the same question more than once if they are telling lies and thus this method reinforces their answer.