How did the crusades contribute to the end of the middle ages?

The main way in which the Crusades contributed to the end of the Middle Ages was by encouraging trade and the exchange of ideas between different regions of the world.

During the Crusades, European knights travelled to foreign lands, particularly those of the Middle East .They were in contact with many different cultures and types of people. Upon their return, they brought new ideas to Europe, causing an enormous change in the continent. New ideas led to new theories, new inventions, and even to the recovery of the lost knowledge of the Greeks and Romans. This influx of knowledge and information gave rise to humanism and the Renaissance.

“i think it is very plausible that if there are five votes to end the death penalty, it could be with the people who are on the court right now,” - smith

so basically it is not clearly and consistently imposed

the communist manifesto is an 1848 political pamphlet by the german near the end of the manifesto, the authors call for a "forcible overthrow of all existing social conditions",  ..