I agree I think the Lucchese’s did the killing to appease the Gambinos after he had killed their guys. As for his body it was easier to just get rid of it. As others have said no murder investigation if he just disappeared. The Gambinos did something similar around that same time with Anthony Plate who was going to be on trial with Neil. The Gotti crew not only got rid of Plate but got rid of his friend and even his car so nothing could be traced back