Why weren't they grateful?

In that instant, Caro says, everything became clear. “When I heard that line, I said, ‘Oh, that’s what this book is about,’” he recalls. And he didn’t just know how the book would end—with a description of that day’s event, ending with those four words. He could see—“in a flash,” he says—how everything he had learned and everything he was still to write would lead to that point. “I knew in that moment how to do the book. And I remember going back to my office and writing an outline as fast as I could. I was abbreviating words because I wanted to get all the words in there.” With each subsequent book, Caro has needed to know where he would end before he could launch into writing it. https://www.smithsonianmag.com/history/rifling-through-archives-legendary-historian-robert-caro-180985956/

The line was “Why weren’t they grateful?”. A line uttered by Robert Moses’ men alluding to the public’s ingratitude towards him.

Both quotes speak volumes about both men. The attitude by Moses’ men and himself show how the power had truly taken him to a place where he could not comprehend the actual feelings of the public

As for the quotes from Caro, they show his working process. How he wanted to have the end in mind so the entire book could work its way towards the final destination. The article is overall a good read showing his process and what it really takes to be a great writer