I believe it is related to this movement to subpoena big tech about “collusion with government” https://www.cnbc.com/2023/02/15/jim-jordan-subpoenas-alphabe...

Either she is being blamed, or she is deeply guilty and wants to try to avoid the publicity, or they anticipate this will become extremely ugly.

Or sundar is blaming her for lining him up for a firing squad.

Or she is a liability due to her past work.

Regardless, it seems like she is leaving because what she had to do to make the government happy previously is now going to be used against Google.

Someone else mentioned the theory that she might be the best Sundar replacement. Maybe she found out it’s not her or Sundar is eliminating competition here.