Rashi: Since they are not from an esteemed family, they will strengthen themselves to find grace [in your eyes].

Radak: It is lest the soldiers get haughty when they see the kings leading them. Put officers, so they will fight stronger.

Malbim: Perhaps Yisrael won due to a miracle of Elokim. Or, it was because the kings drank with you in huts; they felt that their honor is like your honor. Officers will lead the army, and not drink wine!