LBJ believed that Castro was behind the assassination. He was afraid of Castro. He stopped the CIA attempts to assassinate Castro that the Kennedys were reportedly behind. LHO liked some of JFK’s actions on civil rights, etc. But it appears to me that LHO was squarely against JFK’s policies regarding the ongoing actions designed to destabilize the Castro regime.
The BOP and Cuban Missile crisis were a big deal. If Oswald didn't hate JFK after those well documented confrontations between the US and Cuba, what in 1963 could've changed his mind? And there's no evidence that his opinion of Kennedy changed.
LBJ was a bigger anti-Communist hawk than JFK. He also favored escalation in Vietnam while JFK resisted.
So with that in mind, I don't see how Oswald might've concluded that eliminating JFK would change US policy towards Cuba.
Per Det. Will Fritz, Oswald acknowledged during his interrogation that he didn't think LBJ's policies would be different from Kennedy's.
As you mentioned, Oswald was a strong supporter of the Civil Rights Movement. I think that, not Cuba, is what fueled Oswald's hatred of Gen. Edwin Walker who led violent demonstrations again Integration...