How does this document explain how Islam spread so quickly?

This document shows how there were many modes for religion and ideas to be spread to surrounding cities. The writer believes Islam spread due to the trade routes, and how merchants gave each other better prices than they did for non-believers.

Explanation:

the dust bowl, otherwise known as the dirty thirties, was a huge dust storm that killed multiple (and i mean  multiple) farmer's crops, leaving them homeless, and foodless, and jobless. in california, there were 5.7 million residents, and the population shrank as mexicans were repatriated. however, when the dustbowl happened, a lot of people began to move to california. by 1940, 250,000 people had arrived. therefore, your answer would be  the population increased, massively.  i hope this !

explanation:

john maynard keynes developed new economic theories in response to the stock market crash of 1929. great depression of the 1930s. first and second world wars. economic boom of the 1950s.