@Lash,
You are mistaking 30% of Republicans polled with 30% of Americans polled.
BTW - The RCP average for Trump is 23.4% not 30%
Securing 23% of the vote will not win anyone the nomination. There are 14 other candidates splitting 77% of the other votes, and I can only imagine a share of Carson's support moving to Trump should the doctor pull out of the race.
Many of the people who say they like Trump really mean that they're very happy to see a candidate say F-You to the media, and, to a lesser extent, the GOP Establishment. What they might do when it comes time to pull a lever in a primary election remains to be seen. They also like that he doesn't care about political correctness, and see him as a champion in this regard. They are tired of taking grief for saying what they believe to be true things because of a minority of a very loud and obnoxious PC Police who seem to wield more power than they could ever deserve.
A guy in the Army who is scrapping by on too little pay to support his family and who does very well in a work environment that is more integrated than most in this country doesn't want to get scolded about "white privilege" if he says "All lives matter," or "Cops lives matter."
The same thing is true for a lot of white working class folks who very much resent the constant assertions by Progressives (including the MSM) that they are ignorant racists clinging to their guns and religion.
This is the classic audience for a populist and that, above anything else, is what Trump is.
One of my oldest son's friends is a real wild-man. He drinks heavily, is outrageous in terms of the things he says, will do just about anything to gain attention and laughs and is very funny, very intelligent, and very successful in his sales job.
Everyone loves Bobby because he's great fun, and there are different rules for Bobby than for others, but Bobby once told me that every time he dates a girl it starts out great with them saying "Oh Bobby you're so funny!" but it eventually ends with "Bobby can't you ever shut up or be serious?"
The people who are currently supporting Trump are like the girls who date Bobby. Right now it's great fun, but eventually Trump will rub them the wrong way.