One possible explanation for that development is that Islam is a religion that contains more structure then Christianity in general. And poor people tend to actually need structure in their lives, someone or something that tells them how keep away from sin and such. And since we today have quite a few poor individuals in the world I’m not surprised that Islam has taken over as the no.1 religion.

Another theory regarding this subject is that Christianity has lost is power in the developed countries, and how should it then be able to indoctrinate new believers? It’s not like the USA is trying to force Christianity up on the people in Iraq as the old imperialist states used to do.