Conclusions are for citizens to make once they see the evidence, regardless of whether it harms the chances of powerful people maintaining their grip on power.

I've already covered it in a different thread. It's most likely that the DNC leaks were from an internal source.

Assange implied Seth Rich. The emails that were leaked were largely about the DNC railroading Bernie to favor Hillary during the primary. That's not some state-level propaganda. That's how party politics work. A disgruntled Trump supporter would have little reason to leak RNC emails, since it was publicly known how much they hated him and since Trump won in spite of the RNC's antagonism.

Honestly though it doesn't matter who leaked it. It was standard faire political controversy. It was a much bigger deal that Clinton herself maintained a private server to conduct state department affairs. Hard for her to spin that one on the Russians though.