I don't always agree with asdf1234 but he is correct in saying that there are many other profit centres in operating an airport than just passenger flights. SEN has lost its MRO capability recently, to be completed when Inflite close next month, their freight activity is minimal, their corporate aircraft movements are modest and they seem to have actively discouraged general aviation movements and residents. No substantial new hangarage has been built since 2008 when Stobart bought SEN, despite them designating several location on the airfield for this. Rumour had it that they didn't offer attractive enough packages to conclude deals with prospective new tenants.
Just take a look at NWI where the hangar infrastructure has grown hugely in the past decade with new or expanding resident companies and it is now a well balanced airport not having to rely solely on passenger numbers.
Passenger numbers and shiny airliners on the terminal stands certainly polish the egos of airport owners but that is not where profitability is to be found, unless the terminal includes a large shopping mall and SEN can never provide that.