Why scale creates durable trading moats

In Part 2, Mark Crandall relives the events that led to the founding of Glencore and Trafigura. Why did Claude Dauphin go his separate way and what was the founding vision for Trafigura? How had Marc Rich already set the vision for the trading houses which would lead to their domination? How has that dominance led to almost insurmountable barriers to entry for aspiring competitors today? And what was it about these singular individuals that led to their success?