By this time, based on the book of Chronicles, these Rechabites have become linked to the tribe of Judah. Thus, by intermarriage and descent, they are Israelite and Judah-ite. And we also learn in the books of Chronicles that various temple and levite functions seem to fall into specific clans, including the one traceable son of Moses, and these Rechabites. But it does look like the levites of Moses are provided a living as part of the Levite class, rather than as the higher priestly class. But isn't clear that the Rechabite members of the Levites are so restricted since, as we have already been told the Rechabite lineage has been preserved within the priestly lines through intermarriage.
More research is needed here.
Then there is the Maccabean conflict. I suggest that these Hasidim come from the more pious families of the Rechabites. They are already wilderness dwellers. Can't be sure. It is a highly ascetic, hierarchical organization of camps and communities, influenced by decades of waging war against heathen, and borrowing heavily from the effective traditions of the zealous Rechabites that already inhabited the wilderness.