Caesar, Machiavelli, ... may have been criminal and powerful people but they were not mafiosi. The maffia is just one (1!) organisation of some Sicilian criminals. That patricular organisation was created during the 1850's/1860's, when Sicily was exporting citrus-fruits to the rest of the world. Big money was included, and some people gathered around Palermo, and they created a criminal organisation, which was very difficult to become member of. I agree the name 'maffia' may be newer, but the organisation wasn't.
What you mean I think is that Sicilians have had a diversion of the law for ages, since they always had a foreign ruler who put many taxes. But that doesn't mean they are all criminals, or even worse: all mafiosi, since again, the maffia is one particular organisation that has greed as it's biggest ...euhm thing.

Others can tell more, and more interesting about this.

What Mario Puzo tells has no value to me. He was very Americanized (didn't know how to speak Italian) and I don't think he knew something about the history of the maffia. He had a romanticized vision on the maffia.