How is Mark an outlier relatively to the sentence you have quoted? He started from 0 and had nothing to show besides the flip flops on his feet and his skills.
The two arguable factors are luck and outside capital. Are you sure luck played such a great factor in his case ? and was his decision to take outside funding at that stage unnecessary?
How many people do you know who started off at an age of 19-20 and were a tech celebrity in 2-3 years? Well I do not know of many hence they are and will be an outlier for me.
A lot of things including luck and timing beside the usual clicked for both Mark and Bill and hence they are where they are today!
The two arguable factors are luck and outside capital. Are you sure luck played such a great factor in his case ? and was his decision to take outside funding at that stage unnecessary?