Well thats the point. Wealthy and rich people get extorted by gangsters and under the threat of death to them or their loved ones, especially their loved ones, everybody pays, no matter who they are.

As for the Merchandise Mart, the mob was there way before the Kennedys bought it. The place housed speakasies and nightclubs which were owned by the Outfit. When the old Kennedy bought the place during the mid 1940's, the mob was still there and by the late 50's and early 60's, they also collected the deals on the maintance, janitorial and garbage services