In terms of tone, quality, and content, the Republican primaries have been the equivalent of reality TV shows. So your question is basically like asking why Snooki was more popular than JWoww on the Jersey Shore. The answer is who cares, just stop watching that crap.
More seriously, Carly did well in polls from her 'strong' performance in the debates. There has been a long stretch from the last set of them - way too long to be on the sidelines with the daily (hourly) clown act that some of the others (Trump especially) are putting on.
Also, Republicans aren't too keen on a woman president at all, but even less so on a woman Commander-in-Chief, so the recent hysteria over ISIS and terrorism do not bode well for her.
Really? Just because the Democrats are happy with a choice between a power hungry lying elitist who won't answer real question or a Marxist hippie who thinks CO2 is more dangerous than an Iranium A-bomb does not make it so.
She is not very "likeable" or "personable" as a campaign candidate. Among the so called "anti establishment candidates" there is Fiorina, Carson, Cruz, and Trump. They're all pretty much on the same page. Trump and Cruz has the edge out of the four of them. Lastly it probably didn't help her when it was proven there is no video of babies with legs and arms wiggling while waiting to have their organs harvested by Planned Parenthood. However it should be noted every candidate lies. I believe what's holding Carly back is her personality. She's comes off as being stiff and lacking warmth. There is no humor or charisma. Those are intangibles that people gravitate towards when voting. If people don't "like" a candidate they're not going to support them.