Here is your periodic reminder that chapter and verse numbers are not original, inspired, or anything at all but a tool to help scholars know what text goes where. The first part of chapter 6 is apparently the end of chapter 5 in Hebrew Bibles. I don’t know exactly when they started to get added, but it was apparently after the first century because the writer of Hebrews cites Scripture with “it is written somewhere”.
The Chronicler spends a long time on the sons of Levi, nearly as long as he spends on the genealogy of Judah. As the people from the kingdom of Judah are coming back from exile, they need to be reminded of the legitimacy of their political leaders, represented in Zerubbabel of the line of David, and their religious leaders, represented by Joshua of the line of Aaron.
An astute Bible reader might notice some unexpectedly familiar names in these lists. However, even as today, names get reused, so just because someone has the same name doesn’t mean they are the same person. Seeing “Samuel, the son of Elkanah” made me think of the last judge of Israel, who anointed Saul and David as kings. However, that Samuel, whose father was indeed named Elkanah, was an Ephraimite, not a Levite.
In addition to the names and their families, the Chronicler reminds the reader of the responsibilities and duties the Levite families had in service to the Lord. Before the temple was built, each clan within the tribe of Levi had different tasks to prepare the tabernacle for travel or to get it set up when the camp was laid out. Once the temple was built, some of these duties carried over, but the distinctions between the three clans became less and less. However, the priesthood always stayed within the house of Aaron.
Your faithfulness to Your people is a mercy we could not merit.