Final answer:
The Crusades were partially caused by the attacks on Christian pilgrims by Seljuk Turks, which fueled a broader Christian-Muslim conflict leading to a series of religiously motivated campaigns to capture the Holy Land.
Step-by-step explanation:
One cause of the Crusades was that Christian pilgrims were attacked by Seljuk Turks. This event contributed to the broader context of Christian-Muslim conflict which prompted Pope Urban II to call for the First Crusade to reclaim the Holy Land. The violent confrontations began in 1096 and lasted until 1291, encompassing a series of campaigns initiated by Western European Christians. The Crusades were also motivated by religious zeal, the desire for adventure and material gain, and the promise of sinful penance reduction.
While economic interest did play a role in the era's explorations, the statement that 'European merchants wanted spices and silks from the East' captures more the aftermath and the motive behind later exploration rather than a direct cause of the initial Crusades. It wasn't until after the Crusades that the more difficult and expensive trade routes motivated Europeans to find other ways to acquire these goods. The attraction towards luxurious Eastern goods was a lasting impact of the contact established during the Crusades.