His reputation has experienced a bit of a rehabilitation, and he has been called one of the first politicians and diplomats in the modern senses of the terms. Clearly, his diplomatic role was important: the Sicilian uprising began the War of the Sicilian Vespers, the "world war" of the 13th century, a key event in the subsequent history of Europe.
His reputation has improved, and he's recognized as one of the first politicians and diplomats in modern times. His diplomatic role was crucial; the Sicilian uprising triggered the War of the Sicilian Vespers, a significant event in 13th-century European history.