Did the Russians interfere in the US election? This is unquestionably true. The DNC did not leak their strategy docs by themselves.
Was Russian interference in the 2016 election decisive? Highly unlikely. Imo, it would be generous to say the effect was marginal at best.
In hindsight the whole thing was pretty stupid; and lines with the Russian government’s increasingly erratic and incompetent behavior. They could have achieved the same end with none of the blowback by just doing nothing.