I don’t think either Rubio or Cruz is “guilty” on this. CNN was reporting that Carson was going home to Florida rather than going on to NH or SC. It’s not that far-fetched to infer from that that it sounds like Carson is quitting. So I think it’s plausible that some Rubio and Cruz people took it that way and went with it. In any case, I don’t think it made much difference in the outcome.
Carson was polling at 10 percent; he got 9. That could be reasonable polling error, or at most the report cost him one percentage point. (At most.)