The original builder of Sheffield Airport (can't recall... was it Budge?) was after the coal deposits and completed a deal with the local development agency of the time for open caste coal mining of the Tinsley area, at the end of which the land was to be tidied up and partly used for an international airport modelled on London City STOL port. This started off in a blaze of council led glory, until it steadily petered out as, sadly, one airline after another dropped out.
Later, when Peel acquired Finningley, with the intention of making it into a major airport, various objections began to surface from the likes of Humberside Airport, Leeds/Bradford and Sheffield Airport and their respective councils/owners, who foresaw a loss of revenue for their local airports if Finningley went ahead.
Peel bought Sheffield Airport so as to remove one objector from that list, at the same time obtaining some prime building land. There was the proviso in the sale that it was to remain operational as an airport for a number of years (7?). The fact that it never made money as an airport then, or now, suggests that Peel see the long term future of the land as being used for something else, when the proviso runs its period, by which time Finningley will be open, leaving Sheffield, perhaps, with a heliport and a 650m strip.
Peel is primarily a highly successful land/property company. They have acquired, or have the majority share holding, in 5 airfield sites (Liverpool/Teesside/Barton/Sheffield/Finningley). They have acquired those sites for the commercial brown field building land which is located within the site boundaries.