I disagree. The crew were expecting (and rostered) to fly to DUS so anything relating to EDI should have raised alarm bells in the pre-flight stage.
You don't know that for sure. My wife, a former F/A, was well acquainted with last minute operational changes. We are not party to what conversations took place between the Captain and dispatch. He was obviously convinced he was now going to EDI and that was that. I certainly disagree with you that he would happily have flown a different SID to the one in the FPL he was presented with.