Keep in mind there are also different types of realtors. Commercial, hard (private money), etc. My mom has owned a mortgage company for decades, but her business is about connecting a network of private investors with borrowers that can't get conventional loans. The value she adds is not just in connecting these people, but also in making sure she matches the correct risk and reward based on the borrower and investor. An example of the deal she might broker would be a contractor that has a plot of land he/she wants to develop or buy and develop into a few houses (e.g. 4-6 houses). A conventional loan may not be possible (it may be viewed as too risky), but private money may fund such a deal at something like 10% APR (expected to be paid off within a few years at most I expect), but the risk is in whether the people borrowing can be trusted to finish on time and within expected costs, and that's something you learn from experience dealing with the people and industry over time.

In a perfect world, some wealthy doctor could just pick someone to invest in and do so, but in reality it's generally a network of 3-6 investors all putting a portion of they money into a deal, and the borrower has done this multiple times over the years as well. Coordinating that takes experience and contacts.