He also had a deeper sense of memory. I was only a contractor and worked with them briefly, but from what I have seen, he was the one most aware of what has been tried before and failed. For example, his team made an impulse decision to outsource some chunks of the platform to a 3rd party app, but he was able to connect a few dots and point out that the 3rd party app uses a SOAP library, which in turn uses an http client lib, which uses something else, which they found to be non-reenterant .. or some such.

The rest would have discovered this later and ended up patching it, while he is able to make good decisions right from the start. It helps that he was super specialized, and done nothing but C++ and PHP, on Linux, for the last 15 years; while everyone else on the team had a broad encyclopedic knowledge of a lot of stuff.