McGee died from an overdose. Dont believe the mob was involved. For years up to her death her so called friends and associates were stilling what she had when she departed from Lefty. She even sold some of her jewelry a few times to get her fix.

Lefty would never get a gaming license as he was not squeaky clean. I wish the movie had dived more into the senator and the gaming commission.

Both Lefty and Tony brought a lot of heat to Vegas especially in the later years. Tony started up the Hole in Wall gang back in 1971, not really an issue for Chicago as Joey Doves was getting his cut from the heists, it was the other bosses and families that were upset, especially Kansas City and Milwaukee, finally Detroit and Cleveland when the feds were putting a lot of pressure on their associates in LV when gang went after every score it could get, before that Tony's crew was selective. Spilotro was only a minor nuisance for the family compared to Lefty.
With Lefty it was doomed as Lefty was an informant. Lefty was supposed to be behind the scenes, after the article was published, he put himself in the limelight because of his ego, now lefty was hell of a good handicapper which saved his life as he was still a tremendous earner for Chicago. If lefty had just dropped that article after it was published and not make a circus, and if Spilotro was on a tighter lease that the Clown and Dove put on him, it would not have gone so bad. The Kansas City wiretap would have still done damage but the families would have scavenged what they could. If the mob had found out Lefty was an informant they would have killed him already. Even with the FBI surveillance and wiretaps, they would have never had gotten to the key people they did, and someone was feeding them information, which is why I suspect left was still informing after relocating to LV.