It doesn't go against their goals, Russia are a far right expansionist virtual dictatorship. Destablilising America through the Republican party and Trump is perfect for them as it weakens America as a power player in the eyes of the world and Trumps and the GOP lunacy is sending countries away from America into Russian and Chinese hands nearly by the day.

It's the same here with Brexit in the UK, Russia paid for Brexit because Britain is the strongest military force in Europe and has strong ties usually to a well goverened America. Brexit weakens Europe and Britain at the same time.

Conservatives are easier to target because studies have shown they respond better to fake news and share it more often then left wing or centrist folk. Also it's easy to whip up xenophobic nationalist fervour.