This is how I've heard it from KLM personnel (and BA was in much the same situation):
Last year they had more initial availability, but were understaffed.
As a result they cancelled many flights at short notice (short haul Europe mostly, and left many passengers inconvenienced and angry).
Eventually they negotiated deals with airports where they could cut their schedules to more manageable numbers, without losing their coveted slots at hub airports.
So they did that, resulting in fewer flights, which were fuller, and so able to charge higher prices with no need to discount.

If all that's true, then it will take a while before all this works through the system and things are back ti something like they were before.