Ask HN: How did Y Combinator become so successful?

Fellow Hackers,

I am interested in the history of YC and started to look around for more stories and insights about how YC started and became what it is today.

There are some resources on the web [1,2] but I couldn't find too much.

As there are some alumni and employees from YC lurking around here, I just thought to ask you to share your stories!

1: https://web.archive.org/web/20140824071024/http://old.ycombinator.com/start.html 2: https://www.ycombinator.com/principles/