Since Azar's not much of a "destroy and pillage" kind of dragon (though maybe he'll talk it up like he is if he's trying to impress someone), he's well treated by locals. Sometimes this good treatment comes in the form of kind words and appreciation, sometimes it gets him free or discounted supplies for his inventive tinkering, and sometimes it's kindness in the form of food. That latter way of thanks ends up being a favorite of the dragon's and it's far too easy for him to start indulging while forgetting (or outright ignoring) the long-term consequences. Thus, all the friendly treatment adds up and leads to the dragon gaining a significant amount of weight. Since he seems incapable of turning down a meal from a friendly face, it keeps adding up until he's practically beached upon his own belly, much to his own embarrassment.
However, despite his complaining about not "looking like a proper dragon" and his declarations that he's going to start losing weight so his paws can reach the ground again, when he's on his own he can't help but smile and enjoy the feeling of how soft and huge he is.

Commission done by the wonderfully talented