Diana was obviously focused on getting her own emotional needs met through romantic attachments rather than focusing on the needs of her children.
She obviously loved her children, and the fact she was physically affectionate is used to suggest that she was emotionally attentive and put the children first. But the fact she was engaged in multiple ongoing romantic attachments would suggest that wasn't true.
Children need more than occasional cuddles.
It's not surprising at all, given she was an emotionally neglected child & married a man who didn't love her at such a young age, that she'd be drawn into focusing on her own emotional and attachment needs through intense romantic attachments.
This was the reality of Harry and William's childhoods before she died. Two parents who yes loved them, but they were not the primary focus for either of them.
Harry will have had a try to make sense of this. A mother who wasn't available, who then suddenly dies and is portrayed to you via the public outpouring as an iconic angel.
That is going to screw up any young boy.
How do you separate yourself from the reality of your parent as a flawed human? This is a process most of us have to go through.
Adolescence is often a time of anger towards parents in the realisation of their flawed nature and how it affected you.
Young adult hood often an emotional detachment time as you feel separated from them in the paths you are choosing which are different and in your opinion superior.
Adulthood is usually when you start to be able to accept parents are just people, they were flawed as are you, your experiences as a child may not have been ideal, but you are now responsible for yourself which includes how forgiving you choose to be.
Harry hasn't been able to do any of this. He's stuck in the emotional developmental stage of a 12 year old who's perfect mother isn't there to look after him against the rest of the horrid world.
He's a little boy fighting dragons.