Why does React exist?

Nobody told me this when I started React. I learned useState. I learned useEffect. I built stuff. It worked. But I had no idea why React existed. I thought it was just what everyone was using. So I used it too. That gap cost me. I was working on a client project — a dashboard with a notification count, a sidebar, and a data table. All three needed to reflect the same data. When something updated, I was manually hunting every place in the UI that cared about it and updating each one. Miss one? Bu