Think about it mathematically — if the majority of women supposedly choose to settle for jerks, how many jerks must there be? For this to be true, jerks must comprise the majority of men. That’s the only way for there to statistically be enough jerks to go around.
Or the alternative possibility: Perhaps these same jerks are the ones dating a plethora of women who find them overly attractive, and thus, keep ending up with them. There is some logic behind the argument that often women ignore the majority of men vying for their attention because they're not attracted to them, which leaves them susceptible to a very select group of men who most likely are going to resonate with the traits attributed to being jerks. Most men I know aren't jerks, but at the same time, most women aren't dating most men that I know, so there's something to be said there for statistics and probabilities.