I found the answers in Ms. Alice Schroeder's book "Snowball" when I was reading it for the second time. Here is an excerpt from the book that explains his success.
"(His passion for money making) had led him to study a universe of thousands of stocks. It made him burrow into libraries and basements for records nobody else troubled to get. He sat up nights studying hundreds of thousands of numbers that would glaze anyone else's eyes. He read every word of several newspapers each morning and sucked down the Wall Street Journal like his morning Pepsi, then Coke. He dropped in on companies, spending hours talking about barrels with the woman who ran an outpost of Greif Bros. Cooperage or auto insurance with Lorimer Davidson. He read magazines like the "Progressive Grocer" to learn how to stock a meat department. He stuffed the backseat of his car with Moody's Manual and ledgers on his honeymoon. He spent months reading old newspaper dating back a century to learn the cycles of business, the history of Wall Street, the history of capitalism, the history of the modern corporation. He followed the world of politics intensely and recognized how it affected business. He analyzed economic statistics until he had a deep understanding of what they signified. Since childhood, he had read every biography he could find of people he admired, looking for the lessons he could learn from their lives. He attached himself to everyone who could help him and coattailed anyone he could find who was smart. He ruled out paying attention to almost anything but business- art, literature, science, travel, architecture - so that he could focus on his passion. He defined a circle of competence to avoid making mistakes. To limit risk he never used any significant amount of debt. He never stopped thinking about business: what made a good business, what made a bad business, how they competed, what made customers loyal to one versus another. He had an unusual way of turning problems around in his head, which gave him insights nobody else had. He developed a network of people who - for the sake of his friendship as well as his sagacity - not only helped him but also stayed out of his way when he wanted them to. In hard times or easy, he never stopped thinking about ways to make money. And all of this energy and intensity became the motor that powered his innate intelligence, temperament, and skills. "
What a remarkable summary from Ms. Schroeder. This reminds me of a great little book by Albert Gray, The Common Denominator of Success. To quote Mr. Gray,
“The common denominator of success – the secret of success of every man who has ever been successful – lies in the fact that he formed the habit of doing things that failures don’t like to do.”
And this, in my opinion, is Warren Buffett's biggest secret.