"Mannachio was in charge for over 12 years virtually un-bothered, he would have been crazy to not make his fair share of guys and leave his mark"

I don't know anything first hand about what is going on in New England, however, it is worth mentioning that what you are talking about is not impossible or unprecedented. I believe that both Scalish in Cleveland and Marcello in New Orleans had large operations that were relatively little harassment and yet neither made a lot of guys and this was part of what caused their organizations to dry up.