Several years ago I heared a conspiracy version (by DG) that assassination of JFK is similar to assassination in Sarajevo in 1914. Assassination of Archduke Franz Ferdinand of Austria led directly to the First World War.
Assassination of JFK had also a purpose to start a World War - a mortal combat between USA and USSR. No mafia, no Communists, no Zionists, no CIA, no FBI, no KGB, no Cubans, no loner. Assassination of JFK was initiated by third party.
Many bonds led from Oswald to communists and USSR but USA prevented the escalation of that conflict. Warren Commission appointed Oswald a loner and it was a wise solution. It sounds paradoxically but the main goal of assassination was not achieved. The peace was saved.
P.S.
Another interest example of political assassination - assassination of Kirov in 1934. The assassin was 'unstable' person inspired by NKVD. The Сourt found him a loner. The direct participation of NKVD was not proven.