Star Wars was from the Adventures of Luke Skywalker. It was about him and he was the main character. Darth Vader wasn’t his father, and there was no long planned out saga of Darth Vader. Vader was Tarkin’s henchmen. With the first film obviously, then Lucas started rewriting from Empire on.

Lucas made it all up as he went. Its very clear he only started writing the prequels in 1994. He never bothered to watch the original movies again to keep continuity.

Fans balked at the prequel retcons when we really should have when Vader became Luke’s father and Leia his sister. Lucas was retconing the Saga all the time. Nothing was planned beyond the first movie. It was a happy go lucky comic book movie, movie serial like the old serials of Flash Gordon and Buck Rogers. A swashbuckling adventure. Lucas had no plans for Vader, the story conference for Splinter of the Mind’s eye lays that bare.