I believe that such is their course of action because of the lack of a good candidate.
Was I an American I would see Crux, Rubio, Hillary, Bernie and Donald like:
A Canadian joke, a Mexican joke, a traitor, a money-poor joke and a money-rich joke.
Now I gave myself an idea, how could you describe jokingly with a maximum of 4 words someone?
Use people like the Mann as a test ground, or even me, since I'm a meme.