Lansky I see a lot like Lefty Rosenthal, I'm not sure they wanted them to get their hands dirty because they were so good at numbers and making money.

Like Frank Costello said in The Departed, "a lot of people had to die for me to be me". Bosses generally don't get to the top without being dirty somehow. Of course you could probably take the Castellano approach, but that could backfire like it did for him too. And just because you are not suspected in a murder doesn't mean you have never killed. During the prohibition days there were so many murders most were not even attempted to be resolved unless they had concrete evidence in which most had none.