Not that there weren't plenty of people who legitimately wanted to see Bernie win but the goal of the Russians was to do whatever made Hillary lose - hurting her campaign directly with hacking, as well as pumping up both her Republican and Democratic competitors. In the US system, spoiler candidates hurt their competitor more than their opponent, so pumping up Bernie is another way to hurt Clinton.
The whole "they just want to cause chaos" trope is true in a sense, but they were very obviously going about it by sandbagging Clinton and pumping up her competition wherever they could. Clinton was very obviously the major-party candidate that would have produced the strongest, most stable US out of that election, and that's really what Russia was trying to avoid, that's the whole "chaos" trope. It's not truly random in the sense of uncontrollable monkeys, it's whatever they think will cause the most damage, and keeping Clinton out of the White House was a specific and key objective. It was quite obvious that Trump was a moron (and very possibly in the early stages of Alzheimer's) and that he'd be the candidate that caused the most chaos.
(Sorry Bernie Bros, but if Bernie had won the primary, he would have been an easy target for Trump and the Russians as well, and even if he won the general the country would have been highly polarized, even if his actions would have been a lot better than Trump's. People in that timeline wouldn't have gotten to see the mess Trump caused in this one. His continued campaign sandbagged Clinton into the general and was a major contributor to Trump winning. The primary was obviously over and Bernie dragging it out was doing nothing but weakening Clinton. And I say this as someone whose personal politics most closely align with Bernie's, out of the three, and who voted for him in the primary.)