Sociopaths make great first impressions. They are exciting, dynamic, charming, even electrifying. No one is better at seduction than a sociopath. Back in the days before birth control, this meant that a sociopath was likely to spread his seed more widely.
To call people manipulative is to disparage them. But most successful manipulators are that way because people don't recognize them for what they are. And the ability to hide one's true natures is another sociopathic specialty.
Sociopaths are dishonest, disloyal, and treat others inhumanely. In the long run, these traits cause others to seek revenge. But a sociopath would be good at making his exit before his true nature was discovered, but after he had impregnated a few females.
(This is why so many serial killers have been characterized as "drifters." They leave places as soon as their acquaintances -- or marks -- catch on to their true character.)
Their percentage is key. If sociopaths were, say, 20% of the population, people would be more familiar with them, and be on their guard against them, perhaps to the extent of assuming everyone to be guilty until proven innocent (of being lying, conniving, backstabbing, irresponsible, hypocritical, and downright evil).
Another evolutionary benefit of sociopathy is narcissism. (All sociopath are narcissists, even if only a relatively small subset of narcissists are sociopaths.) Narcissism boosts confidence, which in turn can help performance. When it comes to swaying others, having the right body language is crucial, and having enough confidence can often make the difference.
For a man, there's little genetic payoff to being shy around women. (There is a benefit to being fearful in general, but that is a different quality.)
Sociopathy could be viewed as simply another evolutionary strategy. It's a high risk strategy, since people will want their revenge on you. But it's also high reward, since before others try to exact their revenge, you're more likely to have planted your seed widely.
Perhaps the fact that it is a more viable strategy for men than women (whose reproductive capacity is limited) accounts for the fact that the incidence of sociopathy is generally reported to be three times higher among men than women.