The Mafia and most, if not all organized crime syndicates, started as a way for people to defend themselves from abusive governments, officials, etc. Mafia thrives by getting along with people, not openly prey on them.

Syndicates also tend to be patriotic, in the sense that they are defending or at least looking to preserve their interests where they are rooted.

Mafia tends to arbour great disdain for police and similar forces. They can be useful if bribeable or somehow coherced to look the other way but they are still police. The enemy.

I’ll give you an extreme example.

In Brasil, the Comando Vermelho is one of the largest, if not te largest, criminal organization on the country. They are well known for their extremely violent and cruel methods. Yet they are the biggest employers in the areas they control. They build schools, pay people for their work (mostly unrelated to criminal activities), distribute food, run clinics. They act as de facto police, courts and punishers, to keep peace. They nearly replace the state because the state nearly abandoned the poorest of poor, amongst who they set grounds, in the favelas.

I can’t imagine the resistance they would pose to an invading force.

And, I can’t confirm this, but I have a memory of reading somewhere that during WW2, the Mafia helped the Allies infiltrate areas.