Who did franklin d. roosevelt persuade to approve the establishment of the executive office of the president in 1939?

Congress

Franklin D. Roosevelt was able to get Congress to pass the Reorganization Act of 1939. This act was based on the recommendations of a panel of experts, known as the Brownlow Committee. The Reorganization Act laid the groundwork for the large and complex staff the White House operates with nowadays.

nothing certain is known about what happened, but it seems that the country declined gradually, perhaps due to bad government, or, more likely, due to a series of bad harvests, which resulted in widespread and recurrent famine.