If the Podesta and DNC emails came from a leaker (not a hacker), then this story is part of a cover-up to bolster the (false) claim that it was hacked.
Assange said many times the emails did not come from Russian sources, and I think he said they came from a “non-state actor” e.g. a private person.
So 1) a government hacked and gave them to a person or 2) a person hacked or 3) they were not hacked at all but stolen by someone inside the DNC and handed off to Wikileaks.
No one hacked the system long enough to download that much data. Someone copied it locally and provided it