Prior convictions are not relevant to whether a person committed a crime. They have to convict based on evidence. That’s not unusual.
I guess the evidence wasn’t strong enough to convince a jury.
True. He either did the crime or not.
As for the OP, I don't think your upbringing should have much bearing on your sentencing. Everyone has a sob story, especially if you're into criminal activity. People raised properly very often aren't going around committing theft and assaulting/shooting people etc. Most people who get into trouble with the law have some kind of problem in their upbringing or have mental/emotion issues.
This guy needs a really good therapist and a mentor to help get his life and behaviour straight. If that happens in jail or outside jail is up to the courts and the evidence.