Just off the top of my head, I would have guessed that "on the curve" might be a big factor, since it's been stated here quite a few times that platforms on curved track are, if not actually totally forbidden, seriously discouraged for new stations due to the gaps between the platform and the train doors.
If the station had been part-funded by the owners of the mall rather than the owners of the business park, it probably would have been built slightly closer to the mall. Curvature would be an obstacle at some locations along that stretch, but not at every possible site. One would hope that if the mall was the real driver behind the station then a bit more thought would have gone into linking the station to the main mall building.
Over the years since the mall opened there had been numerous suggestions of building a station- be that a typical WYPTE "flatpack" job like nearby Cottingley, or a much more substantial structure on the electrified Wakefield line on the other side of Dewsbury Road (with an accompanying Meadowhall-style "sky bridge).
Frankly this whole affair needs to be documented in detail, and taught in universities as a clear example of how
not to manage public transport infrastructure projects.