It was a bit more than that. The pictures being posted were in many cases literally lifted from other social media profiles or web sites belonging to someone who did not consent or even know their picture was being used here. Occasionally that involved celebrities or semi-celebrities, but mostly just attractive young women, as you said. The "take a picture with a sign" thing was, originally, more about identity theft than anything else. After all, if there were no picture at all, there would be no hawt boobs to attract votes.

Later, it was latched on to by some trolls and control freaks to start to demand pictures as a sort of sad power dominance game. That game was allowed to go on too long.

Agree with your conclusion of course.