Yep watching that clip in retrospect, it makes it clear why this dude was winning. When he points out its nothing but donors in the audience, the media and of course the audience acts aghast. But your average voter at home is thinking "finally, someone calling this shyt out".
Bernie took somewhat of a similar stance to Trump here post-debate
But even Bernie Sanders doesn't have the completely IDGAF attitude as Trump to do it mid-debate and not only that, expect to receive boos in response to doing so and not giving a fukk. Despite all the "divisive" talk regarding Bernie, relatively, he is still trying to remain cordial to the side that wants to destroy him to some degree.