Lyndon B. Johnson was initiated on October 30, 1937 in Johnson City Lodge No. 561, at Johnson City, Texas, but completed only the Entered Apprentice, or first, of the three Masonic degrees. For this reason, he is not included in the gallery(of freemason presidents)
It is strange that Kennedy was killed in LBJ's state, and LBJ became president.
But using a secretive organization such as the CIA or the Freemasons would be a way to execute a conspiracy (if Kennedy's assassination was one of them).
Certainly, there are some strange tales of the Mafia and Kennedy at that time (Marilyn Monroe and the Mafia, and Marilyn Monroe and the Kennedy's, and the death of Marilyn Monroe).