Final answer:
The question lacks context to explain why a Prince would propose at the end of a masked ball. Generally, masked balls in literature allow for liberating interactions that can lead to romantic gestures, such as a proposal, but specifics depend on the story's events and characters involved.
Step-by-step explanation:
The question does not specify which Prince and which story or play is being referred to for the masked ball scene. The excerpts provided offer glimpses into different literary works, each with its unique set of characters and plots, but none directly answer the question about why a Prince would propose at a masked ball. In the absence of a specific context, one can only generalize that in literature, masked balls are often settings for dramatic encounters and romantic proposals because they create a sense of mystery and allow characters to interact in a more liberated way, shielded by their disguises. The prince might be moved to propose due to a compelling attraction, the enchanting atmosphere of the ball, or a significant moment that occurs revealing the feelings between him and the lady he is proposing to. Nevertheless, a precise explanation requires knowledge of which Prince and event the question is about.