I call shenanigans on the claim that Aleynikov was single handedly running the trading infrastructure for even a single one of their desks. That's complete nonsense.
As for Jim Simons: It's generally believed that the main cause of Renaissance's success is that they have a couple hundred of the world's smartest people all working together. It's not a 'key man' shop at all. (Also: You seem to be suggesting that Simons himself did all the work. The fact is that he spends most of his time smoking cigarettes and handing out wads of cash.)