Well part of the story is surely the long delay between the original application in 2000 with a planned opening in 2001, to the reality of construction not beginning until 2007, and not opening until 2009, by which time of course the 2008 financial crisis had hit.
Contemporary news reports definitely seem to suggest the station was conceived, and pushed through sustained planning objections, to primarily serve the airport. It was specifically sited to be the quickest route by road to the airport, with passengers conveyed by a dedicated shuttle bus.
One can speculate therefore that its initial backers, the TOC and local council, were initially aiming for a wide catchment area, with Sheffield to the north, Leicester to the south, Stoke to the West and Lincoln to the east. Maybe they were even hoping it would draw flights away from Manchester, Leeds, Birmingham, Luton and Stansted. The turn of the Century was after all the point when the Middle East started to grow its airlines.
It's only once the project got taken over by Network Rail and called into a government enquiry, that serving the airport starts to look like an afterthought, and emphasis is seemingly being placed on it's wider public transport and green travel benefits, specifically it's benefit to locals and as a parkway station. They push the idea it's a an 850 capacity car park five minutes from the M1 with peak trains to London every 15 to 20 minutes. Also that it will be a Park & Ride terminal serving Nottingham, Derby and Leicester, relieving congested city roads and bus station car parks.
Tellingly, by the time people have noticed it is serving a tiny fraction of the passengers using Nottingham station, the TOC is disavowing original passenger forecasts by its predecessor, while suggesting the recession is also to blame. It even points out that the situation doesn't look quite as bleak once you include passengers transferring from Megabus coaches arriving from northern cities for onward travel to London. Network Rail is also pushing the idea demand forecasting is not an exact science, and things will pick up.
The shuttle bus was long gone, with calls for a monorail by a local MP looking quite Simpson-esque in hindsight. The original TOC were surely hoping to downgrade or even shut the station if or when it proved there was sufficient rail-borne demand, to be replaced by a new station at the airport, served by a spur to the main line.
An interesting side note: there were even quite concrete plans to use it as a park and ride for Donnington Park, which was going to be redesigned to host the British Grand Prix from 2010 and wasn't going to let anyone park at the circuit.