Complex sentence: Jack didn't want Matt growing up hating his mother for leaving them and decided to tell him she died when he was little, from then on Jack raised Matt as a single parent by becoming a boxer and doing the best he could to support him.
Split into simpler sentences: Jack didn't want Matt growing up hating his mother for leaving them and decided to tell him she died when he was little. From then on Jack raised Matt as a single parent by becoming a boxer and doing the best he could to support him.