ABC(C)D. Dreyfus is in between Bunge and ADM in terms of revenue and quite influential in Africa and some parts of Latam (Cargill is the outsized one, twice as large as any of the other and culturally quite different). Continental (now ContiGroup) is about a fifth as large as e.g. Dreyfus so doesn't quite count.
I would recommend the ageing, but still relevant Merchants of Grains [1] for a better understanding of the dynamics of this industry. More modern books - such as Marc Rich's biography - are too sanitised. As you hint, it can't really be "disrupted" by technology - the advantages these companies have are more geopolitical than informational. My position reporting platform in the late 2000s dated from 1994 and had never been updated; despite 5-6 layers of control, some faulty trades (e.g. FX hedge the wrong way) were not caught for months. Some heads of trading desks could negotiate with ministers profitably, but had trouble understanding simple derivatives.
[1] https://www.amazon.com/Merchants-Grain-Profits-Companies-Cen...
And in a way, isnt the way our farming is a national security tool kind of a secret? Like, “merchants of grain” is a niche book thats borderline conspiracy territory, and politicians dont talk about farmers as national security.
https://www.amazon.com/Merchants-Grain-Profits-Companies-Cen...