The reality is the opposite of what Trump claims. When these hedge fund guys trade, they are not just haphazardly shifting paper around. They are shifting paper as a means to transfer wealth and reallocate risk. Nor do they do it in a self-contained universe. They have paying clients who need accurate information and reliable execution to enter into transactions essential to their business survival.
In countless ways, the financial system—and the bankers and hedge funders that are participating in it—supports the so-called real economy. Start with the simple notion of liquidity. People need to have access to cash and cash equivalents all the time to pay bills and to make investments and gifts. It is those hedge funders who organize complex payment systems—credit, debit, electronic funds transfers, and more—that allow for literally billions of small and large financial transactions to take place every second of every day.
Perhaps these bankers did not build this country by laying down the bricks and mortar for various roads. But even an ignoramus like Trump should know that the scarce commodity in setting up these systems is the architecture and design that allows for individual transactions to go effortlessly forward. The fact that no one pays these transactions any mind is a tribute to how well that task is being done.