Valencia v Gerona
Gerona airport has historically been used for holiday charters. Barcelona is about 90 mins drive away and has a large airport supported by a hefty city population. One can think of Gerona airport as really a sort of overflow facility for Barcelona that happens to be near some beaches. The area that's nearer to Gerona airport than Barcelona is largely rural
Valencia on the other hand is a large city. Not quite as large as Barcelona, but definitely a big city none the less. It also has a large airport.
Unlike with Girona, where originating passengers are few - and thus an airline cannot get bi-directional traffic, Valencia is a commercial centre, has the tourist attractions, is on the coast, and has locally originating traffic.
The Valencia Govt know that a Spanish regional carrier like Air Nostrum needs to have significant operations at Valencia and will stick with it for the long haul. Ryanair does not need Valencia. Whether the regional Govt gives a subsidy to Air Nostrum is debatable (there may be a public service need to ensure flights to places in Spain), but under EU law it would be extremely difficult to justify taxpayers money going to Ryanair. Would it be justifiable for Birmingham council to subsidise Ryanair ?