What are some reasons for the spread of Islam?

Question

Also what did the byzatine empire preserve?
why where the middle ages referred to as the dark ages?

Answer 1

Islam is a religion that has far more relevance for certain people than Christianity, which has often been used as a tool of oppression. Mostly it was spread by the byzantine then Ottoman empire as was behind much learning and technological advances.
The Middle Ages are not refered to as the Dark Ages. The Dark Ages were the period after the fall of Rome to the 11th century and are so called because we don't know much about what happened due to a lack of written evidence.

Answer 2

God's messengers spread the same principles of belief; mainly to worship only one God, the creator, that's why Islam spread because has the answers of every body needs to know!

Answer 3

1. Migration, cultural diffusion
2. it preserved roman culture in it
3. death