One Of the first reasons was the art of successful trade around the world.An example is “Vast camel trains,bearing pieces,Perfumes,Precious metals,Ivory,and Silk filed through the town, headed north on the way from Yemen...to the markets of Syria,and headed east from the Red Sea across the desert to Iraq.”(Doc A)
This shows that trade impacted the spread because they took precious thing and when they got there they talked about the Message and I think the people must have loved it.Furthermore,Trade was a big impact in spreading Islam around the Globe.