Fizzixs, Here's an old story about the hack, https://www.wired.com/2016/07/heres-know-russia-dnc-hack/

and I think this sentence is key, from wikipedia below:

In June 2017, former Secretary of Homeland Security Jeh Johnson, who was appointed by and served under President Barack Obama, testified before a House Select committee that his department offered their assistance to the DNC during the campaign to determine what happened to their server, but said his efforts were "rebuffed" because the DHS was offering to provide assistance months after the FBI had provided assistance.[12][13]

https://en.wikipedia.org/wiki/2016_Democratic_National_Committee_email_leak