Crowdstrike said the evidence that the Russians had hacked the DNC was irrefutable.
You seem to hang your hat on agreeing that the Russians probably extracted the email and prepared a .ZIP file or some other compressed file, but there is no evidence they copied the file from the DNC. Really?
Donald Trump said it was probably the Russians.
In the absence of any other explanation for how the email got to Assange...yes, I think the Russians did it. How many Russians were subject to indictment by Mueller?
There are others who know....the person who brought a thumb drive to Assange knows.
Do I trust Assange? Hell no. As I said before...if he admitted the Russian GRU was his source he'd be done as an independent source of info. You do know that Mueller got indictments for 12 Russian GRU officers, right? I know it is unlikely that they will ever be in US custody, but the point is that enough evidence went to the Grand Jury that they issued indictments.
Mueller Investigation: All of the Guilty Pleas, Indictments | Time
And here is the indictment doc.
Indictment (justice.gov)