Christopher Tyerman dismisses the popular idea that the Crusades were about greed.
There’s a traditional interpretation of the Crusades that they were simply land grabs. This is highly improbable. If you wanted to grab land – if you were a knight in France or Italy or Germany – if you wanted to grab land, why go 2,500 miles to a bare Judean hillside that actually was economically rubbish? There was a religious motivation. This didn’t preclude the fact that you were going to get spiritual rewards and probably material rewards – you were going to be paid to go, for example – but the cost, the initial capital outlay to go on crusade, was huge, many times a knight or a lord’s annual income. So this investment was very heavy. It’s hard to see many people making profits from simply going on crusade. There were attendant profits – if you did get land in the East, or if you were a shipper that had a contract with crusaders, etc. But the motive to going on a crusade was clearly not solely, or even mainly, material. There was this religious ideological purpose, it was “the right thing to do”.