Just to add to this, somewhere between 65% and 85% of the American public has never taken a cruise. That is a huge market. Younger families now are also taking their kids on vacations with them unlike 4o yeas ago when in a lot of cases the kids stayed home. Young travellers today also want the newest and best but don't have the time for week long vacations.
I can remember all the naysayers when Royal added the bigger ships starting with the EX class and then bumping it up to FR and ultimately OA saying there is no way they would fill those ships yet here we are.