Why is it not someone’s fault when they get addicted after choosing to do a known-addictive substance? “Not their fault” certainly doesn’t describe all addicts.
They don’t need to be faultless to deserve compassion.
The more life experience I have the more I conclude that assessing the existence and extent of someone's fault is a pointless exercise. People tend to exhaust enormous amounts of pointless energy stuck in that place.
Your last sentence drives it home. They deserve compassion. Who cares about subjective assessment of fault once you reach that conclusion?
They don’t need to be faultless to deserve compassion.