Well thats good for him then - earning more money during a limited time of a career has to be good for the chap.Why? it doesnt makes sense for him nor us, he wont get minutes here even as he would be third choice. I think Grant has player two games since he arrived 2-3 seasons ago, and if we are looking to challenge De Gea's place then we have Henderson who's young and really promising.
The only thing I can think of is he improved his wages, thats it.
But as for why United signed him? I have no idea. Strange one when we have 2 really good keepers and Henderson as the Heir.