Gustavus did not just invent new weapons; he invented a new way of integrating them. He treated an army not as a gathering of warriors, but as a single machine.
By using copper tubes reinforced with leather and rope, he created artillery light enough to be pulled by a single horse or two men. This meant cannons could advance with the charge.
He required his cavalry to know how to load muskets, and his infantry to understand cavalry maneuvers. This created a flexible force that could adapt to chaos instantly.