I think Lucas was influenced by the Godfather films. The original two films have a pretty rigid ring structure that sees the story come full circle. Both films have a clear midpoint - and the first would have had an intermission after Michael carries out the dinner shooting. The themes are patterned and run in parallel: Vito and Michael both begin their entry into the Mafia with the shooting of two people that they perceive as a threat to their families, and also as an act of revenge.
They both have a false-empire and a false-benevolence (and note there are clear differences to both of these under each don). Both are ultimately responsible for the deaths of their own family members - Vito by allowing Sonny to be Don which in turn sees him fall victim to a trap set up through Connie's husband Carlo. Carlo could have been stopped any time by the Don, but Vito didn't intervene in the mistreatment levelled against his daughter, which in turn compelled Sonny to intervene. Later on in the second film, Fredo is involved in setting up Michael for entrapment. Ultimately Michael has his assassin kill him.
The traps in the films also come full circle. At the start of the second film, Senator Pat Geary attempts to extort Michel over a gaming license. Later on the film Michael's assassin kills a prostitute he is sleeping with while in a hotel/brothel run by the family. Geary falls for the deception, and is later shown showing support for the family for the remainder of the film.
Similarly, Hyman Roth devises an elaborate trap for Michael. He orders the Rosato brothers (who work for him) to carry out a fake assassination attempt against Pentangeli (who works for Michael). The Rosato's tell him they are acting on behalf of Michael - and their bluff works in turning Pentangeli against Michael. Just as Geary fell for Michael's deception, Pentangeli falls for Roth's deception. Both assassination were a lie - one a false assassination, the other a misattributed one.
Vengeance, Deception, and Betrayal all come full circle also. The whole story arch of the Godfather Pt 2 revolves around Roth attempting to take revenge against Michael for killing Greene. The story of the first film sees Michael carry out revenge against Sollozzo for the attempt on Vito's life, and against Barzini for the death of Sonny.
Deceit and Betrayal are prominent themes - following Sonny's assassination Vito calls a meeting of the families, claiming he wants to end the bitter war between them. In reality he wants to learn who is really responsible for Sonny's death, and he wants to arrange for Michel to come home. He learns that it is Barzini, not the Tattaglia family,that ordered the hit. He then stands up and assures the other dons by 'swearing on the souls of his grandchildren' that he will not break the peace, all the while knowing that he is lying. That he really intends to bide his time to take revenge against Barzini. The foreshadowing of this is when Michael is made Don his first act is to remove Hagen as consigliere because he needs a wartime consigliere. Vito then explicitly tells Hagen this was at his request.
Vito knows that the Barzinis will attempt to preempt a move against them by taking out a hit on Michael, thus preventing the family from taking their revenge. Vito foretells that a traitor will come to Michael with plans for a meeting with Barzini. Prepared for this, when Tessio comes to Michael he uses his own trap against him.
In Part II the story comes full circle. Although Michael fends off Roth's elaborate plan for his demise, he himself destroys the family that he is supposedly protecting from Roth. In the same way that Vito had defended the family against Barzini and other threats, but had ultimately caused the harm to his family though his own actions.
It breaks down to the next level also, Vito kills Don Fanucci to free Italian-Americans from his oppression, but then becomes the source of the oppression himself. This is then exemplified when Michael becomes don, for instance when he wants to take back what the family had given to Greene.
I have a feeling that Lucas envied this storytelling and tried to replicate it with the Star Wars films. Ultimately though he failed where Coppola succeeded.
