An adaptation of the Catechism for Young Children in modern English.
Question: What happened to our first parents because they sinned?
Answer: Instead of being holy and happy, they became sinful and sad.
Question: What befell our first parents when they had sinned?
Answer: Instead of being holy and happy, they became sinful and miserable.
Simplifying “befell … when” to “happened to … because”. Also, simplifying “miserable” to “sad” with the added bonus of a sweet double alteration.