I've been following but have not posted.
I'd like to bring something up. One of my earliest memories when I was 4 years old was traumatic. My mother was changing my brother's diaper while I was nearby. My mother suddenly out of the blue flew into a rage, as my baby brother had peed during the changing, the stream reached her face. She yelled and slapped my brother, and afterwards realizing what she had done, cried hysterically. I was frightened to the core. She was otherwise a loving kind mother.
Many many years later, that incident was brought up. When my mother was a teen during the Nazi occupation in Europe, she and her sister were assaulted by soldiers, part of the assault was urinating on them after being beaten.
The incident with my brother years later had brought back that repressed memory that caused her to lash out.
So I'm thinking, that taking care of those two babies may have resulted in violence from some kind of trauma NV had experienced in the past. The genital injury is awful and perplexing. It's possible that during a diaper change the twin had peed, it's possible that NV has a thing about self cleanliness, or whatever may have made her hurt him. It may have been due to something that happened with a boyfriend, a relationship, abuse maybe. Or something else entirely that enraged her about the baby, his fussing, his crying, smell, who knows?
As for the poor baby who died of the head injury, IF she is not telling the truth about his falling out of the bouncer, did she want to hurt him because he was a boy, or some other reason...a few that have been proposed above.
What on earth was the motive, what was Lucy Letby's motive?
Jealousy, resentment, misguided rage towards the babies' parents...her father, the pressure of her studies....
All, IF NV was responsible. I lean to she was.