There appear to be a large number of routes which operate during Jan-Mar 2021, but which cease after 27 March. No, these are not ski or winter seasonal routes. The removal of flights seems to be across the network, and not specific to a single country or few airports
Is there a computer failure or some sort of major reworking of schedules going on ? If not, there appears to be a cull of about 15% of all routes across the network effective 27 March 2021