I am using the daily Bible reading schedule from “The Bible.net” for my daily Bible reading.

Today, I am reading and commenting on Numbers 1-2.

A year after the Israelites had left Egypt, Moses organized them.  I suspect that the organization had begun before this, but that at this point was far enough along to formalize it.  The first step recorded here was appointing leaders over each of the tribes.  Followed by a census of all of the fighting men of the twelve tribes.  Once the count had been obtained, Moses formalized where each tribe would camp relative to the Tabernacle and where they would march when the people moved on.

It seems likely to me that the leaders of each of the tribes emerged over the course of the time they were camped at Mt. Sinai.   The same would likely have been true of where the tribes camped relative to the Tabernacle.  Over the course of the time they were camped at Mt Sinai, the people would have become more organized.  We could certainly debate the degree to which this organization was top down (God to Moses to the people) vs bottom up (the people organizing themselves and acknowledging certain people as leaders).  I suspect it was a bit of both, with some of the later rebellions against Moses being led by people who had gotten followers during this process but who were not part of the formalized leadership which emerged here.