...did it on purpose.
It's more likely they transmitted their own emotional pain onto you, where the phrase hurt people hurt people comes from.
Is it their fault they were hurt before they hurt you? No.
Is it their fault that the person who hurt them was also hurt by someone else? No.
Is it your fault that you're hurt by them? No.
It's all original sin, passed on parent (adult) to child, parent to child.
There's really no one to blame, and if you're going to point the finger, you'd have to go all the way back to Adam and Eve.
Though, since you have free will, blaming is certainly still an option, just appreciate that all you're doing is discharging your pain instead of transforming it into a sacred story.
"If you do not transform your pain, you will most assuredly transmit it." Richard Rohr