I've got to think that in his years in the New York construction business Trump saw a much wider range of human behaviors than the slugs in D.C. do - toadies, suckups, bullies, parasites, etc. Add that to, IMHO, an innate ability to size up people almost instantly and he's tough to bluff.
It takes me back to the stories of his military days. More than one friend told how he stood up for smaller younger cadets. He was extremely well liked by instructors and cadets. “FUN” was the consistent word used to describe him. FAIR was also used.
Yeah, NYC was probably good training but I don’t think anyplace could be worse than DC.