a family full of informants is not strong
it doesn't matter if they make people for the sake of making people
You keep saying things like "infested with rats" and "full of informants." Whether in one NY family, or as a whole, the guys who flip are a very small number compared to the ones that don't. And all the rats in the world won't do as much damage to a mob family as general attrition will.
NY mob has more competition from other mafia families and other ethnic crime groups (Russians, Dominicans, latin kings, bloods, etc.) than other cities that have mob families
There are far more examples of the NY families working with other groups for mutual profit than examples of direct competition.
NY mafia is more diminished than you want to believe
Nobody said the NY Mafia isn't diminished. It certainly is. But not nearly as much as elsewhere in the country.
