Sharing this here for lively and hopefully respectful commentary and thoughts. This video represents one opinion of what happened but I've heard some good arguments to the contrary online, the most common being "pretty much all movies are made or broke by the edit".
Editing is incredibly important. They say a film is made three times: by the screen writer, by the director, and by the editor.
Horrified by the first rough cut, George fired Jympson and replaced him with Marcia. She was tasked to edit the Battle of Yavin sequence, in which she drastically diverted from the originally scripted shot sequence. George estimated that "it took her eight weeks to cut that battle. It was extremely complex, and we had 40,000 feet of dialogue footage of pilots saying this and that. And she had to cull through all that, and put in all the fighting as well." While editing the sequence, she warned George: "If the audience doesn't cheer when Han Solo comes in at the last second in the Millennium Falcon to help Luke when he's being chased by Darth Vader, the picture doesn't work."