The Russians did not hack the DNC. The truthful emails , revealing the corrupt and rigged party nomination process we obtained by Wikileaks from a thumb drive because the data was 3 times too large to move over the Internet .
Does this mean Seth Rich had nothing to do with it? No, of course it doesn't. Just because Russians were snooping and quietly spying for months and months doesn't mean that a totally unrelated activity, a disillusioned young man downloading a bunch of emails one night, DIDN'T happen. I doubt the Russian hackers and Seth Rich had anything to do with one another, or were aware of one another at all.
When Putin says he didn't give the emails to Wikileaks, he's probably telling the truth, because Assange said the same thing. Not the Russians. Doesn't mean the Russians hadn't been snooping around the whole time, though. But any activity, Russians, Seth Rich, whoever, any activity that took place before the DNC nominations and that hurt Hillary has to be looked at as possibly aimed at helping Bernie, not Trump.
And Daniel has a VERY good point in that: helping Trump in 2015, early 2016, would more likely entail going after HIS competition (Rubio, Cruz, Bush), not going after Hillary.