That's even more terrifying. At least when I thought it was a HanaKana thing, the popularity made sense.
Otherwise...it still makes sense, I guess, but more for the reason that a person with the personality of "girl" or "male accessory" would be popular- it's just because they're perfectly subservient waifu material. It makes me sad, really, I can't support this trend of two dimensional 2D girls with the aforementioned personalities being the most popular characters in anime. Worst is, it's not going to go away because they're popular as hell.
...But that's not to say HanaKana is blameless in this, she definitely plays a role in this with Kosaki and other flat characters (not to say that it's a trend with her, exactly, but she certainly perpetuates it).