JFK was assassinated because the capitalist cabal, which had ruled the U.S.
since at least 1913, wanted to regain its stranglehold on the country.

   The Kennedy "assassination has demonstrated that most of the major events of world significance are masterfully planned and orchestrated by an elite coterie of enormously powerful people who are not of one nation, one ethnic grouping, or one overridingly important business group. They are a power unto themselves for whom those others work. Neither is this power elite of recent origin. Its roots go deep into the past.”

L. Fletcher Prouty. (1992). JFK: The CIA, Vietnam, and the Plot to Assassinate John F. Kennedy

   "It is Colonel Prouty-with his background both as military officer and international banker-who shows us concisely that Kennedy was removed not only for his skittish policy on Vietnam and Cuba but because he fundamentally was affecting the economic might of this nation-planet, U.S.A., Inc., and its New World Order. Kennedy undermined, as Prouty fascinatingly outlines, not only the Federal Reserve Board but the CIA and its thousand-headed Medusa of an economic system (CIA: 'Capitalism's Invisible Army'), but most dangerously and most expensively (ultimately some $6 trillion in Cold War money) the world-around economic lines of the 'High Cabal' and its military-industrial complex so ominously forecast by Eisenhower in his farewell address."
Oliver Stone's Introduction to L. Fletcher Prouty's book: JFK: The CIA, Vietnam, and the Plot to Assassinate John F. Kennedy