I find this subject very interesting as well. I think it simply comes down to Genovese/Gambino vs. Anastasia/Costello. The power struggle was eventually going to explode between the 2 sides. I think the selling of the memberships and the Shuster murder weren't the main reasons but added together with Anastasia's general recklessness was enough for him to go.

In my opinion I just don't think Lansky or Trafficante had enough clout to order a hit on a New York boss. He may have been moving in on the gambling rackets and those 2 were happy to see him go and weren't going to stand in the way but like I said I think it was Genovese/Gambino that made it happen.

Also I never really believed it was the Gallo/Persico hit team that did the work. I've always felt it was a job done inside the family with the Armone brothers and Stephen Grammauta.