Now, you might be thinking “wWell, that's easy” and then say something like “They were killed by a volcano” or “an asteroid destroyed them.“ If you are thinking this about dinosaurs then you are wrong. These are all “COMPLETELY” true.
Now I will tell you the “very first reason” that may have been why the dinosaurs went extinct. The very first reason was that the T-Rex game stopped making money. The reason that this would have killed the dinosaurs is that they would have no money to buy the dinosaurs BBQ chicken and salad.