Time for some Latin. Post hoc, ergo propter hoc. After this, therefore because of this. It is a famous logical fallacy in which one attributes causation to a prior event simply because of its time order. Don't do that.
To be fair, there is more than time order going on. Putin really did want Trump to win, but let's keep this more grounded. The Russia hacks did basically two things. They created some bad press at the start of the Democratic Convention, leading to Debbie Wasserman-Schultz's resignation (yay!), and riling up the Bernie twits. Let's take them separately.
DWS was a vile sack of shit who needed to go. The DNC was supposed to remain neutral, and she clearly sided with Clinton. Also, she was just a piece of work, and always has been. What did she do to intervene, though? Basically, nothing. Take away DWS, install and DNC head who was more Sanders-friendly, and Clinton still would have won, but DWS was still a scumbag who needed to go. The Russia hacks made that happen.
The bigger problem for Clinton, though, was that this helped create the impression that the scales were tilted for Clinton, playing into that whiny, little twit, Sanders' nonsense about how everything was rigged. Oh, you thought that was just Trump? Nope. Sanders got there first. When Clinton won the Southern states, Sanders whined about how they shouldn't count because those where Republican states, and only Democratic voters should decide the Democratic nomination. The system is rigged! When he started doing better in open primaries, everyone should participate, not just Democrats! The system is rigged!
Oh, did you forget what a whiny little fuck Sanders is, and how much he pulled that shit about rigged elections? Not me...
And that's what the Russia hacks might have emphasized-- the bullshit complaints of Sanders supporters who thought everything was rigged against them because the DNC bigwigs clearly did favor Clinton.
But they were disgruntled anyway! So, the question-- and this is a big question-- is whether or not the Russia hacks played a big enough role disgruntling easily manipulated Sanders voters to turn them off, swinging a close election. Could it have had that big an effect? Maaaaaaybe, but I doubt it.
But if it did, Sanders made it possible.