As m2w said , connections to secret services/freemasonry.You really think Matteo Messina Denaro can hide this long on small island as Sicily without the support of politicians/secret services/freemasonry. Same goes with Toto Riina & Provenzano who was on the run for 40 years. Toto Riina didn't kill Falcone alone, he was just someone who did dirty work.

Italian police keeps arresting them in huge busts almost every week, but its all street guys that are easily replaceable,they are not even the real mafia so to speak. Also in Italy you are guilty until proven otherwise,so some of them get released after busts. People that are on top and "real brains" behind the mafia hardly ever go to prison ,most of them are totally unknown to police anyways.