Why do you think the Muslims were not able to conquer most of that continent??
Both continents are huge and their people had long-established their own religions.
It is Europe.
Stoopid
because most of the population was christian and did not want to convert, additional to that europe was far away from africa which was where it was spreading.
The reason why the Muslims were not able to conquer Europe was because there were other religion empires already established and had already conquered their share of the continent. The other religions didn't want to convert to the Muslim religion even though it was really similar. They stood their ground and kept their land. Therefore making it impossible or not likely for the Muslims to conquer Europe.
(I think this is correct, I did it off some facts I saw)