Because the Sardinia was always very poor so from 1960s to 1997 born the Anonima sarda a gruop of various gangs focused on the kidnappings for ransom (about 150 kidnappings have been counted between 1960 and 1997).
https://en.wikipedia.org/wiki/Anonima_sardasouthern regions were poor too, i think in sardinia there was not the conditions to develope it in fact the government consider local crime ordinary gangs and not mafia-style group, never heard of a sardinian criminal under 41-bis regime
