God wants a count.
He doesn’t need someone to confirm what He already knows. To me it seems God wants the people to know what the tally is so that they will have the facts together once he starts working His plan.
The first verse of the chapter is God speaking the last verse:
Thus did the people of Israel; they did according to all that the Lord commanded Moses.
Numbers 2 talks about God setting the camp up the way He wants. Last verse:
Thus did the people of Israel. According to all that the Lord commanded Moses, so they camped by their standards, and so they set out, each one in his clan, according to his fathers’ house.
I can’t get caught in the trap of questioning their inability to listen and obey, because I do the same.