^Well it's closer than **** ing Dubai!
Clearly nobody's going to travel from the Trafford Centre, bypassing Sea Life, to get to Blue Planet.
The point, which you clearly have been missing from the start, is that people, in the general area, wanting to go to an aquarium specifically, are not going to go out of their way to travel to a tiny SeaLife in a shopping mall when Blue Planet, regardless of your personal opinion of the place and whether the people you know would travel OVER 40 minutes (what does "over 40 minutes" actually imply by the way? Closer to 40 minutes or an hour, since technically it could be days) or not for it, is in the same general area.
Sealife Manchester will do well because of the huge footfall in the Trafford Centre. Very few people in the area, as in the North West not Manchester city centre, will travel to Sealife specifically.
I'm not sure how to make it any clearer than that.