It's not proven (as in, no verifiable evidence was presented) that it was a "hack" rather than a leak in the first place. The emails could have been leaked by an insider. There is some evidence (albeit very weak: file timestamps) that the leaked data was collected locally before it was sent over. I also find it extremely suspicious that the DNC did not allow the FBI to investigate the "hack", but rather chose a private firm to do so, and not just any firm, but Crowdstrike, one of the founders of which, Dmitri Alperovitch, is a senior fellow at the Atlantic Council, a think tank with openly anti-Russian sentiments that is funded by Ukrainian billionaire Victor Pinchuk, who also happened to donate at least $10 million to the Clinton Foundation.
As to the Mueller investigation: no US person has been charged with _anything whatsoever_ related to collusion thus far. It's all "tax evasion" or process crimes. And he can charge anybody he wants in absentia: it's no secret that governments spy on each other and wage psy-ops campaigns all the time. Heck, Obama even listened in on Merkel's phone calls. Russia is not unique in that regard. In fact it's somewhat unique in how _little_ it interferes in affairs of other countries it has no common borders with.
For a bit of a historical aside to give some color to my perspective, consider that the US helped to re-elect Yeltsin in broad daylight in 1996 (he would have lost to a communist if it wasn't for the US), and was heavily involved in getting Poroshenko elected in Ukraine, also in broad daylight just a few years ago. US influence in Ukraine predates Poroshenko, though: see e.g. Manafort.
So to sum up: I do believe that there was "interference" to the extent proven by concrete evidence such as Facebook spend. I do also believe that such interference is part and parcel of international affairs: the US itself interferes all the time, often in a rather heavy-handed way. I have seen no evidence thus far that the DNC hack was indeed a hack, and not a leak. I believe about 0% of what Crowdstrike says, given its affiliations. I don't really believe in "alleged intrusions in voter registration systems" in absence of independent evidence. As far as I can tell it's fake news.
