A few reasons...perhaps since we were so far into the debate (2 hours plus) people took a break and started looking for polls. Thats actually what I did and then voted. Also, his supporters are pretty locked in and are going to find ways to vote for him to continue to drive his numbers up in any forum. Lastly, I know this sounds strange because Trump has many who find him unlikeable, but the average person watching this likes Trump and despises all the rest of the candidates. For example, Rubio gave some really good answers, but he always comes off sounding like a rehearsed politician. Even Cruz, who I think is very solid on almost every issue has a tendency to at some point in every answer come across as inauthentic and a politician. Then you have Kasich, who is so clueless as to the political environment, making reference to the fact that he was winning elections in the 1970s. So all in all at the two hour point, I think most people had checked out of the debate and coupled with the fact that it was obvious that everyone was gunning for Trump, went over and voted for him. He is at 60% on the time.com poll as well.
Luntz group loved Carly. Dear Lawd!