Even though Facebook has only been around for 6 years, don't forget the years of him working on programming.
If an engineer who has worked for several years on the field, but finally gets a big project that's completed in a year, you don't throw away his previous experience and say that he's just a lucky guy who landed a big job. It's the sum of all the work before that adds up to the current experience now.
Only if you assume there are few others who haved worked for several years on the field. If that's not the case, then you have to attribute at least some of the success to luck.
If an engineer who has worked for several years on the field, but finally gets a big project that's completed in a year, you don't throw away his previous experience and say that he's just a lucky guy who landed a big job. It's the sum of all the work before that adds up to the current experience now.