To be honest, it started innocently enough. In fact, this was the series that was never meant to be a series, starting with a book called We're All Animals. In it, I explored a character named Chase Jacobs and his coming of age problems that led him down a dark path that linked up with the people he now refers to as his associates. Of course, it had to be introduced slowly, carefully and in such a way that showed how people could find themselves in this world even if it was never their intention.
I love writing from an alternate POV rather than the more common ones used in books. It's interesting to explore a character that is normally viewed from a third-person perspective, instead, showing all the dimensions and exploring the many layers. It's very easy to just throw everybody into a simplified category but it takes a little more effort to consider where that person came from, what their experiences have been and what drives them. People are vastly more complicated than some writers would have you believe.
There's also something invigorating about sinister characters. It can be quite addictive and fascinating to write about them. It allows my imagination to go to all kinds of dark places that you simply can't explore with a primarily law-abiding and 'good' characters. And if you do, it becomes the central theme of the book rather than a component. For example, if a 'good' character kills another character, it becomes the plot, with the protagonist attempting to understand and justify their behavior. If a 'bad' guy kills someone, it's not such a shock and just becomes another event in the book.
And at the end of the day, when you're a writer, shouldn't you be searching for different scenarios, alternate voices and most importantly, intriguing storylines that aren't following the same, tired format?