#7 – Anakin is Made Military Liaison
It was always a little weird that Anakin didn’t have more real power to be corrupted by in the real Episode III. Putting him basically in charge of a Jedi council who’ve just spurned him is a perfect situation to encourage some power abuses and let us watch Anakin become more hateful and aggressive.
The position also establishes the relationship between Palpatine and Anakin that’s seen throughout the original trilogy: Palpatine is the big man in charge, but Anakin/Vader is the one carrying out the military vision on a grand scale.
#6 – The Order 66 Alternative
Piggybacking off of that, we get the change to the fall of the Jedi. We love this for a few reasons in addition to the ones that Barryte laid out in the video.
The big thing is that it preserves some mystery about the decimated Jedi. A battle that basically cuts the head off the Jedi order is a reason that the galaxy would accept about why the Jedi have all but disappeared, and it gives Vader cover for his Jedi hunt between Episode III and Episode IV. It makes it look like the Jedi weren’t the competent peacekeepers they professed to be, and makes statement’s like Han’s about “hokey religions and ancient weapons” make a lot more sense. To the general public, why were the Jedi defeated? Oh, they were obsolete relics who got caught out by a war. It makes the new military look welcome to boot.
Basically, it’s thematically more satisfying and also feels more like a real historical event than a sudden, synchronized genocide.
#5 – Mace Windu’s Death
The final point in this train of thought, it makes Mace Windu’s death epic to the viewer, but emblematic of how the entire galaxy will see the Jedi Order. Mace is supposed to be one of, if not the most skilled fighter in the entire Jedi order. So to everyone on the ground (and the viewer), he goes out in a blaze of glory, fighting nobly for the cause of galactic peace and defense of the innocents.
But to those who weren’t there, they say, “Look. Even the most powerful of the Jedi couldn’t swing the tide of battle.” He’s the forgotten martyr of the prequel story.