I'll use one of HRC's quotes to respond to you. "At this point, what difference does it make?"
In one sense, none. It is clear that the DNC "put its thumb on the scales" to try to get Clinton nominated over Sanders.
The party structures are not supposed to do that. Now, I think it is somewhat naive to think they don't. I mean, the people running those structures are involved in politics. So of course they play favorites, and that is true of both parties.
But this comes at a time when both parties have elements within them that are sick of that occurring. Its really not so much that it made a difference here in terms of who would have won the primary. Its more that it is disheartening to the voters to think that they have little or no voice in choosing the nominee.
On the GOP side, I can't recall which state it was, but Trump and his people were furious when it emerged that the delegates were chosen by, again, people already in the system and with ties to various candidates.
Now back to the original issue. There is an investigation going on into whether Russian state agents did this. Apparently, there is strong if not overwhelming evidence of it, according to the technical people on such hacking. That is not to say that Trump had them do it. I think that is really far fetched.
But it is to say that the Russians have incentive to interfere a bit and play some games because they strongly prefer dealing with Trump rather than Clinton. Forget the Trump quotes about admiring Putin, that's not important. But, Trump has made numerous statements suggesting a willingness on his part to back down to Russian aggression in Europe.
The question becomes, in the foreign policy debates, how does Trump deal with questions about this. Is he just arrogant and dismissive, smirking at it? I think that would be a mistake, because many commentators on both sides are noting this desire on behalf of the Russians to get Trump elected. That is going to raise suspicions as the next few months unfold.