I don't really know if there is much to analyze. The guy went to Stanford and had the priviledge to meet other great folks with the same passion. His connections and this environment is what made him successful.
First of all, most people who went to Stanford don't found an Instagram.
Secondly, anyone can now apply to YC and make connections with great people.
In my opinion, applying to YC and hoping to get in versus having staff members on university campus with connections to students who now operate prestigious tech companies and being able to walk the same path they have are 2 entirely different experiences.
The process begins with opening the level editor in Doom II.
Or in my case, Warcraft.