Those things didn't come around by accident. It's because the OS was ruthless in cutting off applications from hardware resources, because its compositor was designed for basically moving a textured quad around the screen with very little latency on a mobile GPU, and because its main animation system ran in a high priority thread way above your applications.
All these little things are what made it feel "magical" to use the first iPhone, to have your finger perfectly tracked when pinching and panning on a mobile computer in the palm of your hand. It can't be overstated how important it is for a human to get an instant visual response to their touch, and how highly iOS prioritised this exact thing.