The Kennedy's had many Mafia/organized crime ties....Joe Kennedy got his money from boot legging and that money got JFK into office.

Lyndon Johnson might garner a look over as he had big ties to American Steel companies which made tons of money in Vietnam much like people look at Halliburton in Iraq. Vietnam was a winable war but drawing it out meant more money for the companies that supplied materials for the Armed Forces. So the Vietnam War which was in full swing in 1963 might have been a reason to knock off JFK.