A big factor for early employees (not N. 1 or 2, but the first XXXX) is purely being lucky to be in the right place at the right time.
https://www.independent.co.uk/news/world/americas/stroke-of-...
This was 2007. Now worth 15 times more.
The Chef as well: https://en.wikipedia.org/wiki/Charlie_Ayers
paid 26M USD in 2009. Now worth 15 times more.
So half a billion USD for this.
(same for Nvidia or OpenAI employees just riding the wave)