The mob killed him because he made RFK the AG. Sam Giancana almost certainly played a role in getting JFK elected in the first place by rigging the vote in Chicago. A number of former associates have claimed that he openly declared that he had "his guy" in the White House, and in return he expected JFK to call off his brother. Instead, he put him in charge of the Justice Department and gave him free reign to go after the mob. Giancana was furious.

There's also quite a lot of evidence that certain intelligence agencies had previously worked with Giancana and other mobsters on ways to remove Castro in Cuba. The mob wanted that just as much as the government did, so they could have their casinos back.

The mob killed him because he made RFK the AG. Sam Giancana almost certainly played a role in getting JFK elected in the first place by rigging the vote in Chicago. A number of former associates have claimed that he openly declared that he had "his guy" in the White House, and in return he expected JFK to call off his brother. Instead, he put him in charge of the Justice Department and gave him free reign to go after the mob.

There's also quite a lot of evidence that certain intelligence agencies had previously worked with Giancana and other mobsters on ways to remove Castro in Cuba. The mob wanted that just as much as the government did, so they could have their casinos back.