My theory is that black people are especially vulnerable and will die from Ebola in comparison to Europeans for example.

It has to do with the surviving the black death/pest and the HLA system of the survivors in opposite to the population which never had been confronted to the black death before.

There are some few articles where they collected the HLA specifics of the Ebola-survivors. So, it is still not enough to be sure, but in my guess, if more data is collected, it would show that this is true.