I don't understand how anything in this research is in any way accurate.
In my experience, real trolls, people who torment others for their own gain, are nothing more than bullies, who in turn do what they do, not because they enjoy it, but the effects that come from what they do. So they don't necessarily enjoy belittling someone, but it makes them feel more important by comparison, whereby it would seem the conclusion is that they don't know the parameters and extent of self-confidence and derive their self-worth at the expense of others instead of from themselves.
Then everything mentioned in the article can be derived from those simple terms. Trolls are not necessarily narcissistic, psychopathic nor sadistic, they're just insecure tw*ts. Isn't that equally probable or indeed much more so?
Side note, psychologists reaching psychology conclusions and making things a lot more complicated than they need to be, seems just an inherently human property as a means to reinforce their own beliefs and feel more important/complex as opposed to simple, not entirely unlike trolls.
All this would then mean trolls are important in that they help expose our insecurities, challenge us and would help us grow if we took that opportunity and that they're just a part of "growing up", relating constructively to opposition etc.
But what do I know? I'm just trying to understand this weird and wonderful world of ours and relate to it in an increasingly constructive manner.