"I spoke to you at that time, saying, YHVH your ELOHIM has multiplied you. How can I alone support your bother, your burden, and your
arguments? Take wise and understanding men for yourselves, who are known to your tribes, and I will place them at your head. You answered me and said, 'you have told us to do a good thing.' And I took the heads of your tribes, wise and understanding men, and I placed them as heads over you, ministers over thousands, ministers over hundreds, ministers over fifties, and ministers over tens, and police for your tribes." (Deut 1:9-16)

There is an implied rebuke in the appointment of judges over Israel -- Moses is reminding the Nation of Israel of their sins. For even though they were given the news that they would enter the Land of Israel without fighting for it, nonetheless they could not stop bickering and arguing -- to the point that every group of ten needed its own personal judge.

Why was there a minister over every ten people? Because even then, disputes were so common that ten people could keep a judge busy.