When you say less law enforcement heat theirs 2 ways to look at it.
Either bosses like Marcello and Scalish carefully took steps to keep things on the down low or law enforcement
At that time just simply didn't have enough intelligence
And manpower to dedicate the time take on OC.

I think anytime a boss can run a family for 30 plus years
It's apparent everyone is getting their share or he's so respected and feared nobody dared make a move

I think Marcello when you at history should considered as one the better bosses in that conversation

One thing about those smaller families like New Orleans and Cleveland (Scalish years)the violence was kept to a minimum.