RWY in sight, your version is not quite correct either (the crew did not knowingly ask for and secure a landing clearance to Brussels). It's a long story which I've explained on more than one occasion here on PPRuNe and frankly can't be bothered to repeat yet again.
I found one of them from another thread on the ATC forum:
Just for the record, the Northwest into Brussels was essentially an ATC error. Enroute ATC had him on their strips (incorrectly) as going to EBBR and thus vectored him as such. Both EDDF and EBBR were landing on 25L that morning. When the crew failed to identify the LOC (having set up the FRA frequency) they asked appr for the frequency, which was given. Thinking it had changed and they had not received notification of this change, they set it up and landed on 25L - at EBBR! For sure a more alert crew should have picked up on lots of little clues. But remember, it was after a long eastbound overnight flight and the crew were being vectored by ATC from TOD onwards. More knowledgeable controllers, including those at EBBR, should have known that NWA didn't operate into EBBR and could have sought confirmation of destination.