Why is Moshe and Aharon’s response to the complaint at Mei Meriva different than their response to other complaints? Apparently Moshe and Aharon had expected the Second Generation to act differently than the generation they had led out of Egypt.
While Moshe and Aharon are silent, but God responds to their next complaint by sending snakes to attack the nation, but this time the people take responsibility and attempt to repent, acknowledging their sin and asking Moshe to pray for them. As a solution, God commands the creation of the Bronze Serpent (Brass Serpent). Bnei Yisrael eventually learn to believe in God, and finally act independently, when they sing the Song of the Well, and rally to conquer the land of Sihon.
Inspired by Rabbi Amnon Bazak's shiur - listen for more.