It is accidental - he strokes her hair too hard, forgets to let go and breaks her neck in the process. Similar to how he kills the mice and the puppy by mistake, this is also a circumstance where he underestimates his own strength and doesn't realise how what he is doing is wrong. When he is stroking her hair, she tells him to let go, but he panics and instead of doing so holds on.
She then begins shouting and screaming as she is scared, which makes him angry as he doesn't want anyone else to hear or else George will angry with him - George told him not to talk to Curley's wife so he is desperate not to get caught. When she doesn't stop screaming, he keeps holding on, still panicked, before his shakes her and her neck breaks. Also: "Her body flopped like a fish." - same as Curley when he gets his hand broken - "Curley was flopping like a fish on a line.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.