Whatever else you can say, Hillary was not channeling a lot of enthusiasm outside of a very narrow group.

It felt like there were weeks in peak campaign season where she wasn't touring or making speeches. What even was her signature issue? (Considering how she was associated with the abortive attempts towards universal health care during Bill's term, that would have been a sensible focus, but I don't recall it mentioned once)

The whole campaign reeked of "play to not lose" rather than "play to win". She assumed she was the annointed favourite, guaranteed the win, and that's not really going to excite uncommitted voters. Bernie, at least, generated buzz.