Small margins are more easily manipulated by bad actors. As awful and destructive as the Koch brothers and Adelson are, they’re still Americans and they’re not autocratic heads of foreign states with long experience in disinformation, propaganda, and kompromat and with access to the kind of talent and resources a powerful nation-state has. I don’t think Putin is due one iota of influence in an American election, but perhaps you disagree.
Xeni and the rest of the Happy Mutants have also done extensive reporting on campaign finance, gerrymandering, voter disenfranchisement, and other GOP cheats, long before the 2016 election season. That the authoritarian head of a powerful foreign state would demonstrably support the Republican efforts last year (along with right-wing populist efforts in other countries) is a new and noteworthy addition to the dysfunction of American politics, but again, perhaps you disagree.
That Clinton and the DNC are trying to use the Russian interference to deflect attention from their own bungling and corruption (which BB has also reported on and which most of us also deplore) is not surprising, but that doesn’t change the indisputable fact that the Russian interference occurred or that other liberals and progressives should find it more disturbing and deplorable than it seems you do.