Hilary Clinton has been suspected of using her position as Secretary of State (2009-2013) to benefit the Clinton Foundation. She may have used her private email account to transact business that she did not want the public to learn about through FOIA requests.
The House Select Committee on Benghazi subpoenaed her emails in 2016, but her IT staff deleted them all and 'bleached' the hard drive so they could never be recovered. Now it appears that he goofed, and used a Google Drive account to transfer those emails. Google may have a backup copy from all those years ago.
Google has been a staunch supporter of Hilary, especially during the 2016 campaign. Let's see what they turn over.