They write letters... to God.
There are indeed serious issues out there, ones that specifically impact Millennials and would need to be confronted by either Democrat as president. Yet if we're to believe The Atlantic, many of the young people vociferously supporting Sanders, collegiate and otherwise, don't question him on those issues; they simply have a vague notion of Sanders as the "most liberal" person running. More than that, though, they've created a cult of personality around Sanders and have turned him into a kind of weirdo folk hero: the guy with the wild hair and the Brooklyn accent who preaches fiery sermons about how they're being kept down and it's time to rise up. He listens to them and empowers them, so they reward him with their loyalty and idolatry, making them far more like Donald Trump's outraged acolytes than they'd like to admit. And sure, a vote is a vote, but in the end it's support awarded for largely superficial reasons, even if, ironically, they flock to Sanders for his "authenticity." They've made Bernie "cool" and that's a self-fulfilling prophecy in which students exponentially adopt Sanders as their candidate because, well, that's just what you do when you're a member of the collegiate left in 2016. It's what everyone does.