AI-version:
Investigative journalist and assassination expert Gus Russo maintains that elements of the Cuban intelligence service (known as the G-2, or DGI) likely encouraged Lee Harvey Oswald to assassinate President Kennedy in retaliation for continuous U.S. plots to overthrow or assassinate Fidel Castro.
Russo, along with other researchers, argues that Oswald—a fervent Castro supporter—traveled to Mexico City in September 1963 and made contact with Cuban diplomats and intelligence operatives. According to Russo's investigations (detailed in his book Live by the Sword), members of the Cuban regime were made aware of U.S. attempts to assassinate Castro, and they may have in turn accepted or encouraged Oswald’s offer to eliminate Kennedy.
Russo's research builds on declassified documents and interviews with Cuban defectors. For instance, a controversial 2006 documentary co-authored by Russo (Rendezvous with Death) further alleged that Cuban intelligence contracted Oswald to carry out the assassination.
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Gus Russo's book "Live By the Sword" can be read online here (you'll need a free account for full access):
https://archive.org/details/livebyswordsecre00russNowhere in the book does he make any of the claims stated above about G-2/Cuban intelligence meeting Oswald and encouraging him to shoot JFK. Nowhere. Don't trust me, just go to the address above and read it for yourself. You can do a quick search for "G-2" or "Cuban intelligence" and be taken to those sections. You'll see that Russo never says Oswald met with Cuban intelligence and/or they encouraged him to shoot JFK or informed or inflamed him and that led to him shooting JFK.
What Russo
does say in the book is that there were numerous rumors and allegations that Oswald
may have met with either pro-Castro people or, more important, Castro's agents (note the huge difference between a person who was pro-Castro versus a Cuban agent/officer). And that in these meetings they may, again
may, have told him about the covert war on Cuba, the assassination plots, and that the Kennedy Administration may have been readying an invasion of Cuba. Finally, as a result of these supposed meetings Oswald was angered enough to strike back at JFK. However, Russo also admits that Oswald may have learned on his own about some of the above anti-Cuban efforts and then acted on his own without any influence, directly or indirectly, from these pro-Castro people. Most important in all of this is: Russo admits he simply doesn't know.
Russo's complaint is that these rumors or allegations were never fully investigated. That's his main argument. Why? For a number of reasons: fear of a possible war that would follow, fear that the assassination plots would be revealed, fear that intelligence sources and methods would be exposed, fear that the "Camelot myth" of JFK would have been destroyed.
Here's a good summary (page 347) from the book of what he believes may have happened (again, note his qualifiers):

In any case, I gave the link to the book. You can read for yourself what he argues.