Here is a fantastic farewell message that Seth Klarman wrote on Buffett's retirement for The Atlantic,
How Buffett did it?
https://web.archive.org/web/20250000000000*/https://www.thea...
Buffett's Alpha: http://docs.lhpedersen.com/BuffettsAlpha.pdf
tldr; he was leveraged with good stocks
That link isn't loading up for me.