Answer:
1- High religious fervor, usually in the form of violence specifically towards Jews and Muslims.
2- Split and decentralized internal factions - usually a crusade would consist of several separate armies compromising of different ethnicities which would usually bash heads with each other. Note: Led to the formation of multiple crusader states such as Principality of Antioch, Kingdom of Jerusalem, Country of Edessa, etc ...
3- Usually led by minor and regional nobles seeking glory and the establishment of their own fiefdom. Typically 2nd or 3rd sons who would not get the family inheritance.
Step-by-step explanation: