Or are you asking what took me fifteen years to understand?
Dan basically planned the whole thing. When the whole thing was too big, he would break off a piece that wasn't and develop it as a wholly separate thing.
I understood this strategy worked, but I didn't fully understand why this strategy was successful until I realised source code matters more than I thought[1]: If your program is short enough, there won't be any bugs in it. This is why learning how to read and write dense code[2] can make your programs better -- and that's what I learned how to do[3].
[1]: http://www.jsoftware.com/papers/tot.htm
