The chance that CAX has got is that Stobart's want to build a road haulage depot on the site, but they will only get planning permission from the LA as part of a scheme to develop the airport (and that is looking dodgy).
At DTVA, there is already an operational airport and there is plenty of scope for development. I'm sure Peel would love to have a successful airport there as it will make their life easier with the LA's, but unfortunately it's losing too much money while the property development market is tanking.