So Episodes I - III were on TV this weekend and I caught most of them again after not seeing them for quite awhile and they hold up rather well when it comes to motivations and character development in ways this new film really doesn’t IMO.
Whatever you think of Hayden Christensen’s acting ability, his turn toward the dark side is clearly within character. He loses his mother. He is infatuated with Padme. He desperately wants to be recognized by the Jedi Council as a full member. He has visions of the woman he loves dying painfully. He is always somewhat distrusted by the Jedi save Obi-Wan and Qui-Gon. All of this leads to Palpatine’s ability to turn him and it happens clearly when he slices off Dooku’s head while saving the Chancellor even though he hasn’t recognized it yet. When the eventual Emperor offers him the possibility to save Padme through use of the Dark Side of the Force (which is clearly against the Jedi belief that things must die so life can be renewed), that’s the thing that puts him over the top to become Darth Vader. He’s selfish that way partially because he’s done so much for the Jedi Council before that and they’ve shown him zero respect. Yoda seems to know that this was always a possible outcome. He failed to control it (because let’s be honest, people make bad decisions for love), much as he intimates to Luke in the current film.
The thing about those three films that this one sometimes slips up on is there is really strong characterization of all the people involved in this Galaxy redefining fight for control. There are real stakes that are evident beyond just “First Order Bad. Resistance Good.” And yeah, I see that they’re kinda implying more shades of grey in The Last Jedi, especially through the Vegas Planet scene, but it doesn’t hold up so well in a Galaxy where the Force requires balance and there are white and black hats, even when they may change sides eventually as Vader himself did twice.