I think the cape idea was a Sarah Brightman thing, I've seen her have something like that on a few clips.
Also, I think he wasn't quite himself tonight. Not just the singing, but the little chance he got to talk? There was something different about him.
I think he went on knowing he had no chance. I would be interested to know if that song choice was down to him. Surely at the rehearsals it would have been apparant that this song wasn't working for him? And what happened to the singing lessons that contestants had been meant to be having? I didn't see any improvement in any of them.
Just edited this to add, that I think the cape was a concession to his love of Sarah Brightman, and if he had been choosing a song, he would have chosen one of hers. It was never him that mentioned Freddie Mercury first, it was other people. He likes Sarah, and Meatloaf.
He was totally mishandled by BGT.