There's an almost dream-like quality to the story of how this particular company came into being, as if it were designed as literary device in a novel about life and love in the hay days of silicon valley but underneath all that a lesson of how guaranteed success drives us to unhappiness as if the gods see to it, for their entertainment but to serve as a lesson to the rest of us monkeys. Sounds more like soap opera than corporate history, though it's all about human drives, feelings, aspirations for power and control, and there will always be the voyeuristic aspects to watching someone cast their personal fortunes onto the most promising water, and waiting for fish to rise...big fish...before the bait falls apart or is nibble away by small fry. I wouldn't bet that 4 million dollars feels like small change to people just because they have far more than they can spend. Our human sense of wealth seems to be related to having some notion of what we can do with it and not just how much we have left, because there can never be too much, let alone enough.

I've enjoyed this review and the disscussion here in the comments section. It's a period of history that has so many compelling aspects to it including the archaeology and genetic history. 
As to motives for the movements of people considered here, do none of the theories take into consideration the changing climate and the impact of herding cultures and their land-us practices on the hydrologies and ecosystems of landscapes that could not support them in great numbers as their success brought about population increases? I'd heard that mentioned in a lecture many years ago long before the current climate concerns regarding AGW.