Why does the Torah name the Nasi of Merari before saying where they camped? For Kehas and Gershon, it names the Nasi of Merari after saying where they camped!
Moshav Zekenim (23): Gershon and Kehas camped in the west and the south, near the Degalim of Efrayim and Reuven, who are called Bechorim. Merari camped in the north, near the Degel of Dan, a Ben Shifchah, so the Torah delays saying where they camped.
Malbim (22): The Torah also mentions first the primary matter that it comes to teach. For Kehas and Gershon, it primarily teaches where they camped, so that is first. For Bnei Merari, we know that they must camp in the north, so it primarily teaches the Nasi. 1
We do not yet know if they are in the east! The Torah teaches that Moshe and the Kohanim are it is not the east only in verse 38! Perhaps it was known that they will be in the east, by the opening of the Mishkan, or because the east is most esteemed (Yehudah was in the east). (PF)