I'll break this down for you.
1) Barr testified that he DID NOT KNOW of any problems Mueller would have with Barr's conclusions. Namely 2 points of:
a) There was no collusion..
b) There was insufficient evidence to charge for obstruction of justice.
2) Pelosi then said "Hay, Mueller sent you a letter saying he was concerned!"
a) Without explaining what she thought Mueller was actually concerned about.
b) Assuming that saying "I don't know or I do not recall" to the Congress is an impeachable offense.
3) When the facts came out about what Mueller was actually concerned about, it made Pelosi look silly to anyone other than her rabid base.
a) She needed a win so the media could spin a fake narrative for a few weeks.
b) She needed to send the message that is Barr digs up any dirt about unauthorized spying on a presidential candidate that she has 6 ways to Sunday to get back at Barr.
Got it?
Good!