The bernie supporters, the children they are, were not told how the game is played. They were (and still are) wasting their energy and $$ attacking TRUMP now, instead of attacking clinton now.
From what I've seen while lurking at
Democratic Underground, a lot of Progressives are really afraid - yes, afraid - that Donald Trump will win the Presidency. I haven't seen one post therein which optimistically compares Mr. Trump to Barry Goldwater (1964).
Presumably, they figure that Mr. Trump will blast away his unfavourables like he blasted through his Republican-only unfavourables over the past eight or so months. Really odd! As of now, Mr. Trump's general unfavourables are higher than Sarah Palin's were ~4 years ago. At that time, there was one DUer who posted on the Sarah-Palin-as-nom subject: "I smell...1964" (if she had won the Pubbie nom for '12)
Go figure! Mr. Trump has got them scared deep...
...and he just might swing his unfavourables around if he gets the nom...