But if a referree is scared of the mafia or other criminal organisation, of course they'll always be afraid to do this.

This is the central point. Some newspapers, the pink one leading the way, are trying to convince us that the collusion between the mafia, Inter ultras, players, and club officials was not such a serious matter after all.
They are attempting to push the narrative that, yes, the rule prohibiting direct relationships between players and organised fan groups was broken, but that everything can be resolved with just a couple of match bans.
But the mafia is involved here! The mafia, through the ultras, was doing business with the Inter world by reselling tickets at ten times the price, managing the San Siro stadium car parks, the market stalls, and even the club’s official merchandise.
The mafia had every interest in ensuring the team won as much as possible. Players who refused to renew their contracts, like Skriniar and Lukaku, were made to meet the ultras to be pressured with threats, followed by defamatory media campaigns.
I am fairly certain that such methods have also been used over the years with referees.