A number of observations can be made:
First, God caused this in Artaxerxes. So far in the book, we’ve seen that God has moved the heart of Cyrus to release the Jews (1:1). It would be nothing for him to move the heart of another king. In fact, this is what the text says (7:6, 9). Clearly, this is a supernatural event. Solomon writes, “The king’s heart is like channels of water in the hand of the LORD; He turns it wherever He wishes” (Prov. 21:1).
Second, Gentile kings were superstitious of national gods. In verse 23, Artaxerxes says, “Be careful to provide whatever the God of heaven demands for his Temple, for why should we risk bringing God’s anger against the realm of the king and his sons?” (NLT) He may have been superstitious of bringing down God’s wrath—even if he didn’t know that this was the infinite-personal God of the universe. D.A. Carson writes, “From the perspective of pagan superstition, the rulers would not want any of the regional gods angry with them.”
 Carson, D. A. For the Love of God: Volume 2 : a Daily Companion for Discovering the Treasures of God’s Word. Wheaton, IL: Crossway, 1999. January 7th. Ezra 7.