Certainly AG Barr will need to go back to Mueller and his team on this. Either they lied, or someone lied to them. In this case, probably someone at CIA.
If anybody lied to Mueller it was because Mueller wanted to be lied to.
The disingenuous “we were just acting based on the information we were given” schtick is not going to fly it it may be enough to keep some out of jail
“Either they lied, or someone lied to them.”
You left out the third possibility: they never bothered to ask the question, because they didn’t want to know the answer.