I have a young friend—21—who is bright and thoughtful. He was a Bernie fan. Now, he is a fan of nothing at all and will not vote. One of his biggest reasons is that Bernie promised to get money out of politics, and then sold out to Hillary.
What boggles my mind about young, smart—but YOUNG—people is not the idealism or the preference or the personal distaste for any candidate in particular (I am shocked anyone wouldn't like Obama; I am not shocked anyone wouldn't like Hillary), but their comfort level at going from caring very much about something to caring not at all.