Tancredi is your typical charming and handsome Italian boy. He's technically Prince Fabrizio's nephew, but Fab thinks of him more as a son. In fact, he often wonders if he allows Tancredi to get away with too much, like when Tancredi teases him about visiting a mistress and cheating on his wife.
At this moment, Fabrizio thinks, "Really, this was a little too insolent. Tancredi thought he could allow himself anything" (1.80). But time after time, Tancredi uses his sense of humor to get back on his uncle's good side. If you can make fun of an Prince for cheating on his wife (to his face), you can get away with pretty much anything.
At the end of the day, Tancredi is an opportunist who understands what he needs to do to climb the social ladder in modern Italy. As he tells his father, "If we want things to stay as they are, things will have to change" (1.85). In other words, if people from Sicily want to keep living a rich lifestyle, they'll need to adapt to the changing world. The longer this book goes on, the more Tancredi uses his charm to advance himself in society. As the text says,
Tancredi, too, was the object of great curiosity; though everybody had known him for a long time, now he seemed to them transfigured; no longer did they see him as a mere unconventional youth, but as an aristocratic liberal. (2.22)
Tancredi hasn't always been the most beloved kid in Sicily. But he bet on the winning team by fighting with the Italian armies that have conquered Sicily. His strategic mind, plus his humor and charm, are sure to make him a success in the new world. At the same time, there's something sad about the fact that only people like him are going to succeed in the future. After all, not everyone is an opportunist or a schemer.