There are several factors that could cause a personal to develop NPD and its very complex. I will touch on a few environmental factors that could set a child up for this disorder.
Abuse (trauma) can cause a child to be arrested in their development. For example, constantly being rejected, beaten, not shown love and affection, not having their physical, spiritual and emotional needs met can cause a child to be stunted emotionally and not be able to regulate their emotions. In turn they grow up to be five years old emotionally. They become irrational and not able to connect with others or show empathy. They literally stop growing at the age of their trauma.
Over protection of that child causing them not to be able to form their own identity. Growing up in an environment where a child is not able to have a voice or choose for themselves causes anxiety and can also cause the child to grow up as a control freak due to not being able to make certain decisions when they were younger. This can also cause other issues like anxiety disorder and codependency.
Over praise of a child can cause grandiose narcissism. When a parent over-praises a child it causes them to feel as though they are better than everyone else, the child can become very competitive and have a sense of entitlement. There is nothing wrong with healthy praise, but a child must also be told the truth when they are wrong or have room for improvement.
This disorder can also be inherited or taught behavior. Growing up in an environment where abuse was witnessed and having one or both parents that are narcissistic can set a child up to become the same way. A product of their environment.
Having emotionally unavailable parents. I went through this as a child. I was raised by my grandmother, and she did do her best raising me. However, I was a very lonely child and craved attention and affection. I rarely got hugs and my emotional needs were not met. This could cause NPD but it can also cause a child to become very empathetic and in my case, I did not turn into a narc, I became an empath and a people pleaser.
Rejection can be so traumatic for a child that they internalize it and create a narrative within their own minds that they are the best at everything and that they are always right. That when they make a mistake, it is never their fault it is always someone else's fault because they caused them to make the mistake in the first place. This is what a seed of rejection can do in a child's life. They form this protective barrier that causes them to not take accountability for their own actions as adults.
Now, I am no professional and I speak from my own research and experiences. As I mentioned before there are so many factors that could cause someone to development into a narcissist. I would take the information given here and further research for yourself. You cannot defeat something without knowing what it is you're up against.
The bible says in Hosea 4:6 "My people are destroyed for lack of knowledge: because thou hast rejected knowledge, I will also reject thee, that thou shalt be no priest to me: seeing thou hast forgotten the law of thy God, I will also forget thy children."
In Matthew 12:29 we read "Or else how can one enter into a strong man's house, and spoil his goods, except he first bind the strong man? and then he will spoil his house."
Be blessed and stay safe.
Paris