I think Wizzair decided they'd attempt to get the Norwegian Gatwick slots by dumping capacity into the Norwegian domestic market in an attempt to bankrupt them, and then taking the released slots fairly pain free. This is why it was mutually beneficial for Norwegian to sell/give the slots to easyJet. Keeps Wizz out of LGW and nullifies any real reason for Wizz to hang around in Norway, another market which they've failed miserably in (the Norwegian long haul slots at Gatwick would be fairly useless to Wizz).