zra was not just a priest and prophet. He was a scribe. Scribes were men of education and papers. It would make perfect sense that he would have kept careful records of what was going on as he and over 1500 other Jews transitioned from Babylon to Jerusalem. As such, this chapter commences with a listing of the chief men who went with Ezra on that westward journey.
Now, there were a couple of significant things that happened at the outset of Ezra trip. First, he recognized that despite the tax-exempt-status offered by Artaxerxes to the Levites who would go to work in the temple (Ezra 7:24), they did not have any of the common Levites going with him (Ezra 8:15). It was essential to have them going along since the task which they were setting out to accomplish was specifically a holy mission dedicated to the temple of God: Levites were necessary.
The second important thing that Ezra had to deal with was the danger of the long journey. Depending on their route, their trek may have been well over 700 miles. And, according to Ezra 8:31 there would be plenty of threats to their safety along the way. But, the problem for Ezra was that he had stuck his neck out by boldly proclaiming to the king that "God would take care of them." Since he had declared his faith so openly, he felt unable to then ask for human protection from the king's guard (Ezra 8:22). So, he didn’t.