Saturn has a very strong graviational pull, so it’s likely that it captured comets and asteroids into orbit and they collided with each other. They may also have collided with other moons. Eventually the pieces got smaller and smaller from hitting each other and spread out to form the rings.
Most planets pull things toward themselves. I guess some pulled stuff and those stuff got stuck to each other and formed Moons. But in Saturn’s case the stuff that was spinning was not interested in sticking to each other and stayed that way. So Saturn got its rings 🙂