After Innocent became pope in 401, he worked very hard to keep Christians focused on what Jesus taught. Some Christians were making up different things, like saying Adam and Eve’s sin did not affect them, and that Jesus was only a “good example” not the Savior of the world. Pope Innocent I taught the truth about Adam and Eve and Original Sin to help Christians stay close to Jesus.
Read the story of Adam and Eve in your bible. Why did they eat from the forbidden tree? What happened after they ate that fruit? Because Adam and Eve brought sin to all mankind, we all have the urge to disobey our parents, teachers or other authority figures. This is why Jesus died to save us.