We also promote Brazzers content (teasers / sitereviews) on
www.naughty4nature.com and must say that they have top content. However it didnt make any signups by promoting their content but adding and reviewing their clips is always a pleasure :D
About how Nathan/Fabien did it, solo action, partner of an investors group or whatever, what does it matter? The guy is successful.
They did pretty well with their acquisitions and in this speed and strategy they will/are for sure be #1
Probably they cater millions of people with free and paid content and they know what kind of formula works for them the best otherwise they can't do these kind of numbers.
Conclusion, totally not bad for someone who started with coding and later SEO activities.