I've seen some conflicting views in my effort to find the answer to this question and was looking for expert advice. I've seen some theories that it was to stop the spread of Islam west, or to allow an outlet for warriors of Europe that wasn't Christian on Christian violence. Just looking for some clarity.
hi! Not at all discouraging further discussion on the points you raise here, but fyi, you can get off to a great start in the FAQ:
... specifically the first post, featuring /u/ambarenya :