Nehemiah, Ezra, and God all love rules—613 of them, to be exact. In fact, aside from the actual physical rebuilding of Jerusalem, the re-institution of the Mosaic laws and rituals is the main objective of Ezra and Nehemiah.
Since God isn't showing up to eat and chat like he did in Abraham's day, the people experience him by obeying his laws. It wasn't all that long ago that prophets like Ezekiel and Jeremiah were de-emphasizing the role of Temple ritual and focusing more on God's expectations for ethical behavior. That was easier to do when there was no temple and the people were in exile. Now that they're back, this stuff matters again. Plus, since these rituals and laws were to be unique to the Israelite community; it was a nation-building exercise. After this, all other people recognized the Jews as people who had certain rules—they observed the Sabbath, only ate certain foods, didn't intermarry, only worshipped one God, etc. (source). (In this sense, Ezra's reforms were very successful in making the community distinct.)
Questions About Rules and Orders
How do religious rituals maintain order in a society—or in this ancient one in particular?
How about in the present day? Do rituals still play this role?
Why are rules so important to God? What's he trying to accomplish through them?