The International Standard Bible Encyclopedia explains why a cupbearer was such an important official in the royal courts of antiquity. A cupbearer was "an officer of high rank at ancient courts, whose duty it was to serve the wine at the king's table. On account of the constant fear of plots and intrigues, a person must be regarded as thoroughly trustworthy to hold this position. He must guard against poison in the king's cup, and was sometimes required to swallow some of the wine before serving it. His confidential relations with the king often endeared him to his sovereign and also gave him a position of great influence" (Vol. 1, p. 837).
A century ago, archaeologists discovered an Assyrian list of salaries paid to high-ranking officers. In that land the cupbearer received the fourth-highest salary in the kingdom, above even that of the justice of the highest court of that day.
Nehemiah was one of the many lines of distinguished Jews who held high governmental positions. Before him were Daniel, Shadrach, Meshach and Abed-Nego in the Babylonian period. In the Persian era, Daniel again became a counselor of King Darius (Daniel 6:1-2 Daniel 6:1-2  It pleased Darius to set over the kingdom an hundred and twenty princes, which should be over the whole kingdom;
 And over these three presidents; of whom Daniel was first: that the princes might give accounts to them, and the king should have no damage.
American King James Version×). Afterwards came Mordecai and Queen Esther. So we should not be surprised to find a little later that Nehemiah was a cupbearer for a Persian king. GN