It seems like Kiner scored each “act” differently. There’s definitely a Vangelis vibe to the first part, and then Williams kicks back in for Order 66, and then it sort of becomes the Tron: Legacy soundtrack for the next act.
It’s also, looking at what happened in this episode, seeming like Filoni rewrote this final arc as kind of a riff on the Disney Era movies. Episode 1 had a LOT of The Last Jedi in it, and this one is very clearly pulling from Rogue One.