Yep, Bernie is surging because he stands for something and that resonates. Joe, like most of the rest, strategy is to put their finger in the wind and hope the metoo crowd doesn’t cut it off.
Bernie, is an idiot, and his world view is evil and dangerous.
Not that I want to compare him with Trump, but in many ways, I think Bernie's supporters are thinking, "If Trump could have done it, why not Bernie?" And there certainly are parallels between Trump and Bernie in terms of the fact that, as you said, they came out as standing for something, even though in this case, what these two men stand for are polar opposites of each other.