Why did the children of Israel believe when Moses performed signs?
The children of Israel believed because they saw the signs Moses performed. When Moses did what God told him, throwing down the rod so it became a serpent and performing another miracle, the visible signs convinced them. Their belief rested on witnessing those miraculous signs, not merely on Moses' words.
Les teaches that as Moses approached the children of Israel, he did exactly what God had told him to do. He threw down the rod, and it became a serpent, and he performed another miracle. Then Scripture says they believed. Why? Because they saw the signs. Les emphasizes that this pattern runs all the way up through Israel's history. He also notes that Jesus spent three years performing signs and miracles up and down the land of Israel to prove to those Jews who He really was.