Highly doubt that Silva is hungry now all of a sudden... He's a legend in UFC, famous in Brazil, got lots of money... Touching the gold again won't mean much, he's not a 25-year-old kid anymore.
Silva regaining the title won't mean much?
For sure, Silva only signed up for the rematch because he's not hungry to avenge his loss and get back the championship belt or anything irrelevant like that. It must be solely for another big pay day even though Silva already has more money then he knows what to do with.