Though maybe rather than just getting bums on seats, EZY and others will take this reduction in capacity to improve yields to a more sustainable level on their routes, with over capacity already potentially existing to many of the former FR destinations, or neighbouring airports.
When you quote that FR handled 800K passengers from BHD, many of these could well be opportunistic passengers, travelling on day trips or weekends for £10 return. Would be interesting to know per centage of BHD passengers on promotional fares, and average fares from BHD.
EZY and the other airlines operating from Northern Ireland, tend to only offer more realistic sustainable fares, EZY base fare usually about £40 return. So out of the 800K former FR passengers, many may not choose to avail of other airline services as the price is going to be much higher. Those who were savvy could travel many times a year with FR for basically little or nothing, and I personally think the remaining airlines are not proactively chasing these types of passengers.