I was discussing this case with a friend of mine that is an ancient historian, and he mentioned a book called “The Gift: The Form and Reason for Exchange in Archaic Societies” by Marcel Mauss as a study into the phenomenon of power of the kind displayed in this case.
I haven’t read it yet, but my friend explained that Mauss studied how gifts in ancient societies created obligations that bound people together which also implied it could be used as an instrument of power. This seems to perfectly mirror how Dan Williamson used his ‘generous’ loan to effectively bind Livermore and control his trading. I’ve added the book to my reading list, as it seems like it could provide some interesting historical cases for understanding these kinds of power dynamics in business (and other domains in life).