I am a bit of a PG critic myself at times but he became rich from selling his own startup. He became richer by starting YC but he didn't need to start YC. Based on his essays he basically had enough money to be set for life from selling Viaweb and when he started YC he was looking for something to do next other than just retire.
I’m also annoyed when people make the argument that goes: “person X became rich from A he didn’t need to do B”. Maslows hierarchy holds true for all of us. Once he got wealth he desired influence (and power).
