I have seen diferent hypotheses on whether Nitti was the Boss of the Outfit in quite the same way that a NY Family Boss would be of a NY Family-with complete and total control. The Outfit was organized a little differently. While I wouldn't say Nitti was a front boss he may have been something closer to a CEO.

In any event Nitti was the identifiable leader of the Outfit and the one who had led the Outfit into the Hollywood extortion cases. When this went bad (Browne/Bioff got arrested and ended up providing information-at first inadvertently and then on purpose to the authorities), much of the initial post-Capone leadership hierarchy was indicted.

Greatly angered, everyone met at Nitti's house to plan strategy. Being the self-serving sort of people they were a consensus was reached that since much of this was Nitti's fault anyway and since he was the guy out front, he should just take the fall for everyone. Ricca was the leader of this faction and the most vocal about it.

Of course Nitti didn't see anything logical about this and was of the opinion that since it was a conspiracy charge everything would be fine if they just all stuck together. Nitti had been in prison before and had ZERO desire to go back.

Nitti and Ricca started screaming at each other and finally Ricca said "Frank, you're asking for it". This was widely understood to be a threat to either do the time or wind up dead. At that Nitti told everyone to leave his house.

The next day he killed himself.