What does the origin of many of the routes demonstrate about europe and the crusades?

 The Crusades stopped the entire known world (including Europe) from becoming completely Muslim. 

Muslim armies had conquered much of northern Africa, Egypt, Palestine, Syria, and Spain, which had been some of the most heavily Christian areas in the world. 

Thousands, and possibly millions, of Christians died during this drive to eventually bring the entire world under Islam. 

The First Crusade was launched in 1095 by Pope Urban II to check the advance of the Muslims and regain control of the city of Jerusalem and the Holy Land. 

If this defensive war was not fought then we would probably all be Muslim today. 

I am sure that some atrocities were committed by individuals of both sides during this war but by most people's judgment this was a just war. 

The mercantilism option