Why are people in rich countries more prone to covid death than they are in poor countries?

Could it be that they on average reach older age?
Could it be that they have better statistics reporting?
Could it be that they get more ill by breathing in a mask?
Could it be that they have had more lock-downs?
Could it be that they have more doctors and hospitals?
Could it be that they are more vaccinated?
Could it be that they use more pharmaceuticals?
Could it be that they have more life-style diseases?
Perhaps all these factors weigh in?

What does WHO have to say about this?