OK it took me a while to understand what this linked article was saying, and how the simulation makes their point. But I think the Scientific American article linked in the first sentence makes all this more clear (
https://www.scientificamerican.com/article/is-inequality-ine...). It’s titled “Is Inequality Inevitable?” The simulation basically is simulating what this other article is saying, which is that trades that are not equal in value but even just slightly different in value (one side gains more than the other side), will ultimately result in an “oligarch” emerging.
That article concludes that a (completely) free market economy will result in wealth trickling up to a few oligarchs, unless there are methods of redistribution.