How can some authors like J.K Rowling and Stephen King be so successful and make writing a career...?

It wouldn't be weird at all. I dare say any amount of writers, some with all the potential of King, Rowling and others are working in supermarkets, and probably petrol stations and pubs as well.

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.