The thrust of the articles was to call on Trump to release all of the still-secret records relating to the JFK assassination belonging to the CIA and other federal agencies that the National Archives is required by law to release by October. In the Post article, the authors state that they have received reliable information that at least two federal agencies are going to try to persuade Trump to block the release of some of the records. In my opinion, it is a virtual certainty that the CIA is one of those two agencies.
Sabato and Shenon are correct in arguing that Trump should reject any such request. The notion that the release of records that are more than half-a-century old will threaten "national security" — however that undefined term is defined — is manifestly ludicrous.
But then Sabato and Shenon go astray. Like so many others since the JFK assassination, they try to figure out what the motive of the accused assassin Lee Harvey Oswald was. In the Politico article, they posit that maybe — just maybe—Oswald somehow discovered the super-secret assassination attempts against Cuban leader Fidel Castro by the CIA and the Mafia, which had entered into an assassination partnership to kill Castro.