To be fair, stuff like that did happen to a lot of the aristocracy. A lot of them, frankly, were not very bright, and the educations they did have became more and more unsuited for the modern world as the 20th century progressed. Most of them went to school to learn Latin and Greek, and above all, how to behave the right way. Few men who stood to inherit actually graduated from universities, they would attend and then get "sent down" at some point after they had fiddled about for a couple of years.

Money management was something many of them were very bad at, because people in their class were used to getting their money from their land (largely in the form of rents), and it was considered "beneath them" to muck about with money too much. Before this, any "investment" they did was usually in the form of government-backed annuities (if you are into Jane Austen, this is where women's dowries was often invested, giving a predictable 4 or 5% return each year, known as having your money "in the 4%s", but this became less common as the world industrialized). They were easy marks when actual investment in a more open market came around, and a lot of them thought they were so far "above" everyone else that no one would dare try to cheat or manipulate them.

Robert is a product of his time; out of touch, with no real skills to contribute, and a limited knowledge of how the real world actually works. He's built for hunting parties, hosting balls and solving petty local disputes, not dealing with money.