Because opposing a known leftist is so very "establishment."
So if Cruz had 900-some delegates, and Trump and Kasich were the underdogs, would it be wrong, or dirty, or "beltway" for them to team up against Cruz? What's the problem?
It's just a funny little acronym I ran across.
We know Kasich is a statist neocon who is more than likely bought and paid for by the big money guys. He is something of a squishy manlet also.
Cruz has done a decent job of appearing not to be those things except for his neocon hawkishness. Being a US Senator married to a bankster doesn't bode well for future actions on his part independent of the powerful and monied interests.
To be fair, Trump does talk about destroying ISIS like the neocons but in true form he never says how. Of course he isn't funded by the big money guys, he considers himself one of the big money guys. Neither is he opposed to big government in principle.
Still, if we were going to choose who the "kept" men are out of the three; Cruz and Kasich are the ones who are beholden or in sympathy with the establishment, much more than Trump.
At this point Trump still seems to be an independent actor. I'm not sure it is true but that is how it looks. If he would even change or try to make things better as we define it I have no idea.
We have our first viable third party candidate, it's just that he is in the process of subverting the Republican nomination away from the GOPe instead of starting from scratch. Pretty impressive IMHO.