It is often thought that the crusades were attempts by a growingly imperialist Europe to seize the Middle East for economic reasons as well as religious ones (namely conversion) . This however, is not the case. The crusades were intended to be a defensive campaign against a Muslim enemy (the Seljuk Turks) that had seized the holy land and were threatening Byzantium and the Byzantine empire. This is important because the Byzantine empire was a buffer between the east and the west and the west was in no condition to mount a full scale defense. This was because the west was fractured into dozens of pieces. What would later become Germany was divided into over 300 provinces ruled by various princes and dukes and what have you. Had the Seljuk Turks taken Byzantium, Europe would not have been able to mount a defense. Not until the pope called for a crusade was Europe able to prepare. Through Catholicism, Western Europe united and was able to push back the Turks and reclaim the holy land that the Turks had taken from the peaceful Arabs and Christians. Furthermore the emperor of the Byzantines sent a letter to the pope requesting aid against the Turks. Thank you for your acceptance and good luck.
No, the crusades did not save western civilization/culture. They should have gone after the jews instead of muslims. The eradication of jews would be a much easier task at that time, reclaiming the sacred realms of christianity whilstgaining a foothold on the muslim empires would be the next step. Just look at media now, controlled by jews and islamics. They did a good job of controlling the vermin population but failed in the endgame mission.
The Jews posed almost no threat whatsoever. They were an unfortunate minority caught between two massive warring factions. Your argument that the eradication of the Jews would have helped secure the "sacred realms" is flawed. The jews were never really in full control of the Holy Land, it was the Arabs, and then later the Seljuks. The Crusades helped preserve Western Civilization because at the time Islam forbid artistic expressions of the human form. Now take a moment to let that sink in. No artistic renditions of the human form would be taking away a huge part of Western Civilization. There would be no Leonardo Da Vinci, no painting of the Sistine Chapel, no Michelangelo, Donatello, Raphael, Botticelli, and others besides. If the Seljuk Turks had penetrated into Western Europe and gained a foot hold, it is very likely that the works of these artists would not have come to be. A large presence of Islam in Western Europe would also have hurt other regions of study such as mathematics. In the age of the Crusades the Seljuk Turks believed that Allah could do anything and was not beholden to any law ie. the laws of logic. That being said according to their faith, Allah could make 1+1 not equal 2...which is of course impossible. You will find that there not any jews who had such ideas. The muslims also had a history of burning churches, destroying or seizing relics, and killing people who simply did not agree with them. Muhammed had what I like to call a "triple ultimatum". To an enemy Muhammed would present them with a choice: Fight and die, live under sharia law or die, and convert or die. Sharia law was and still is one of the most persecuting law codes in existence. Muslim faith outlines Christians and Jews as "people of the book" meaning that they all believe in the same God but that the Jews and Christians have the story a little wrong. All "people of the book" had to live under Sharia law. Doesn't sound too bad right? Wrong. Living under Sharia law meant you had to wear a specific dress code according to your religion and you were unable to practice your faith in public places for fear that Muslims would hear and become tempted by "infidel worship".