Why Did Nehemiah Trust God In The Past?

1. Queen Esther destroyed the enemy of all the Jews, Haman, who had plotted against the Jews to destroy they, and had cast Pur - that is the lot - to crush and destroy them (Esther 9:24). Therefore, these days are called Prium, from the word Pur (9:26). This is my first time to know this idea.
2. Hezekiah trusted in Lord God of Israel, so that after him was none like him among all the kings of Judah, nor any that were before him (2 Kings 18:5). I was surprised that he was the only person who trusted in the Lord God of Israel among all the kings of Judah. Does this mean that David did not trust God in the past?
3. Nehemiah is a very interesting book, because it uses many like "I" instead of using word like "he" or "Nehemiah." For examples,