It's not so simple. CNN started the story, and it was Carson's campaign that gave them reason to think so. They said he's going to take a break at home in FL. Generally that indicates he's considered quitting. And it was expected that he would quit after IA. It's not like the Cruz people just started the rumor whole cloth to take his votes.
Also, when Carson's camp tried to clarify things, their reason for him going home to FL was that he needed to go get a fresh set of clothes. Seriously?