I suspect this increase is related to the losses and capacity reduction created by the MAX grounding. We'll be paying for that grounding in higher fares for a year or more.
I doesn't really work like that. Supply and demand determines ticket prices. WN (and other airlines) are able to raise ticket prices because the economy is good and planes are full. Now, if you want to argue the the MAX grounding has taken some of the supply out of the system enabling fares to be raised, I may buy that somewhat.