This does feel like the WMD fiasco leading up to the Iraqi war. The media is not really taking time to think this through. Probably a good chance that Russia and China too, have tried and succeeded in infiltrating all aspects of DNC and RNC. However, there's a big leap to now suggest that this information was given to Assange. It's unknowable, so one must guess at the most logical answer.  Assange says it wasn't the Russians and there is no evidence that he has lied in the past. There is no evidence that he has any ideological leanings. His leaks have been applauded by both Left and Right depending on the leak.
No one thought Trump had a hope in winning the election. Why would Russia expose their intelligence for such an unlikely win? Not good spy craft. Finally, do you really think Russia thought Hillary would be a bigger thorn in their side (or more unpredictable) than Trump? Finally, criticizing the Russians for hacking, is utterly hypocritical. Please see Snowden's revelations.