When Cruz was holding on like Don Quixote tilting at a windmill, his fighting on was understandable albeit futile. After all, he was still in second place and the election isn't over and you never know what may happen. But when he decided to collude with Kasich it instantly took him from "party outsider standing on principle and fighting the system" to "defender of the system" status. After all, his whole shtick is that he will never compromise but how does striking a deal with Kasich mean standing on principle? It doesn't, it smacks of "me me me, whatever it takes I'll do".
It made him look small and weak. Bad bad move.
I believer Boehner calling Cruz names was also by design of the GOPE to support the Cruz campaign. They were trying to get Cruz some of his outsider cred back, and they thought hated Boehner could do it.
The problem is that no one gives a rat’s a$$ about Boehner anymore, and no one trusts the GOPE and Cruz campaign beyond trusting them to try to screw over the base.