Why do we fall for difficult people?

Complicated = Interesting to some. "Difficult" people probably tend to be a bit more out-going and confident which for many is a desirable trait. I know it's probably a bit cliche at this point, but many girls would rather date the confident "douchebag" vs the introverted "nice guy". Many girls will put up with "Chad" despite how poorly sometimes he handles relationships socially and emotionally because of the handful of desirable traits he may have hoping they can mold him into something they find ultimately desirable, i.e. the confident nice guy. Or they just put up with his BS because they think he's the best they can do and take him even if he's ultimately toxic when it comes to the relationship. Not to mention the term "nice guy" to many girls has become a bit of a negative stereotype because of incels and introverted guys who struggle to find success in dating and in-turn can have poor attitudes in general towards women or don't know how to really manage the waters of meeting someone new through the initial friendship phase, into dating, and then finally full-blown committed relationship.