BHD is being dwarfed by BFS, and this will have a huge impact on the future of BHD.
Only if your premise is that airports must continually expand. London City is a counter-example; after rapid initial expansion it has settled for the past decade around the 4.5 million mark, rising and falling slightly with the economy but showing no ambition to become a mega-airport.
If a business finds a niche and makes a profit why can't it just exist there? Why the constant demand for growth? Belfast City is point-to-point orientated, unlike Heathrow it doesn't depend on a depth of connections for its value. Perhaps it's as big as it's going to get, and maybe that's just fine.
I do agree that KLM expansion seems overdue. But bear in mind that since the started the Belfast City service they have also introduced the Dublin service which is now double-daily and may have drawn away potential for Belfast. In that regard they are to be commended contrary to their fellow Euroairlines who open a Dublin service and consider that sufficient for 'Ireland' as a whole; Wow, Lufthansa, Air France, Iberia, TAP, Scandinavian, Turkish...