Best answer is that it was personal, but not with the mafia. He was protected by the Genovese after he gave testimony, Nigro wanted to kill him but a few unknown capos said no and it would be better to pull his protection. After that word on the street was the Genovese family washed their hands of him, he was fair game and had backstabbed and cheated guys a mile long. It was a who is who. In a way the Genovese were responsible since they cut him loose, but he had too many enemies that it was only a matter of time before someone would get their hands on him.