Sanders is old. Old people have skeletons in the closet. Sanders wasn't a big deal long enough for the press to have really dug in and started dragging those old skeletons out.
Sanders had a similar message as Trump, just a bit different flavor. That resonated with the voters. I think Sanders would have grabbed more electoral college votes but to win, no idea. Hindsight and all that
Sanders is old. Old people have skeletons in the closet. Sanders wasn't a big deal long enough for the press to have really dug in and started dragging those old skeletons out.