Excellent question.
Maybe because the FBI did not get their hands on the Hard-drives and possibly did not want to as it would blow their false narrative out of the water and reveal the download speed to be too fast if it were a Russian 5000 miles away.
“A group of former US intelligence officials contend that the hack of the Democratic National Committee’s computers in 2016 was an inside job.
The group, which calls itself the Veteran Intelligence Professionals for Sanity, or VIPS, said there was an insider leak that occurred thanks to someone with access to a DNC computer.
The VIPS were formed in 2003 to protest the way the administration of George W. Bush manipulated intelligence to justify the Iraq war, Salon reported.
The VIPS theory relies on forensic findings by independent researchers who go by the pseudonyms “Forensicator” and “Adam Carter.” The former found that 1,976 MB of Guccifer’s files were copied from a DNC server on July 5 in just 87 seconds, implying a transfer rate of 22.6 megabytes per second — or, converted to a measure most people use, about 180 megabits per second, a speed not commonly available from U.S. internet providers. Downloading such files this quickly over the internet, especially over a VPN (most hackers would use one), would have been all but impossible because the network infrastructure through which the traffic would have to pass would further slow the traffic.”
https://nypost.com/2017/08/15/new-report-claims-dnc-hack-was-an-inside-job-not-russia/
https://www.bloomberg.com/view/articles/2017-08-10/why-some-u-s-ex-spies-don-t-buy-the-russia-story
One word:
Seth Rich.
*Assange knows*