The reason why the polls looked like that is simple: In an age where you get socially ostracised and threatened for going contrary to the popular opinion, people are afraid of publicly speaking their mind. These polls are also often held in heavily traficked areas, including shopping malls and campuses. Now, if you are a "millenial" and a group of associates of yours are present whom have a differing opinion, do you really want to openly claim that you are pro-contra? Unlikely, at best you'll claim undecided. If you have observed the social movements of the last few years, you have likely seen it happening: Disagree with the establishment and the establishment supporters will go as far as to call your workplace and spread rumors about you to get you fired.

Honestly if the media didn't stoke the fires so much and lie so much, this wouldn't have happened.