How was the Islamic Faith able to spread so quickly throughout the Middle-East and beyond? Why did it stick in the places it spread? What caused the spread of Islam to finally slow?

where is the rest of the question. this isn't making sense. can you upload a picture of the question?

i believe the answer is: returns on investments, no wages

people who belong in upper class society would most likely get there by obtaining multiple source of income, which a certain percentage of ownership for businesses. since most of them are job creator, they would most likely get their money from profit, not wages.