It's normal in the lifespan of a man-made satellite. A satellite is thrust into orbit at a speed which will keep it in orbit for a long time, but Earth's gravity is still affecting it as it travels, because it is relatively close to the Earth's mass. After a while the orbit begins to degrade, until the satellite can no longer resist the pull of gravity, and it falls into the atmosphere and then to the surface of the Earth. Satellites that generate power from the sun through batteries can stay up longer, but not forever. Scientists watch these satellites all the time, and can tell when their lives are nearly spent, and they warn the public as needed. This has happened many times before, and will again.