I saw a lot of nonsense get spewed on Facebook- things that could be quite simply fact-checked, and people completely bought into them. Also, contradictory emotional appeals were spread (without, of course, the responders recognizing the contradictions). Finally, I was on a forum when someone gave stupid numbers concerning Obamacare, that I quickly checked and challenged (he left and never came back).
Having discovered that people by and large won't think critically about what you're saying, and using the viral nature of emotional appeals to create a general sentiment (which will later be rationalized) payed off for somebody. I don't know if it was the Russians or not.