And don't let anything I write next detract from the fact that I thought it was really, really good.
That's not the way it happened. That is, this three movie series about how Anakin Skywalker turned into Darth Vader is not true, it's not how happened. I don't care if the entire thing happens in George Lucas' world. Sorry. I didn't buy the switch at the critical moment of the film. Lucas blew it and went the wrong way from the beginning. The whole Chosen One was wrong; the whole virgin birth was wrong; the whole slave upbringing was wrong.
How does evil happen? What is evil? Lucas doesn't seem to know. Character is destiny. Evil is the willingness to sacrifice others for your own interests, desires, knowledge and pleasure, a desire and willingness to live for your own glory instead of the glory of God, that is, pride and lack of faith in God's goodness. Pride is the seed of rebellion in every human heart. All sin is rooted in unbelief. The story is old, in some ways the first story ... the story of the fall of man.
Was Anakin proud? Some, but mostly he was a confused kid. His switch seemed too whimsical, a phase. It's believable that a person can do what he did, but it's not the stuff of a trilogy, a space opera. What causes a metanoia — a change of heart?
Good people usually turn bad because of crushing disappointment, and that disappointment turns to lack of faith in the goodness of God. Some people stay there, but others turn vindictive, angry, it turns to wounded pride, a preoccupation with settling the score. Some turn back, but others keep going. They become a relentless focus on self, on wounds to the self and the desire, and further sometimes, to suppress that knowledge, this becomes an obsession to set the entire world right. And some, in this process, get power, and the enormous power makes them mad.
That's not quite the story of Anakin. His love for Padme is too selfless. For him to be evil, she needed to be seen as a thing to him, as something to give him pleasure and as useful to him, even if he uses her on an emotional level. But his love, puppyish as it is, is too real. A being capable of real love doesn't kill a bunch of children to save his wife. And a being capable of real love cannot be held by the forces of darkness to the extent that Darth Vader was. Dominated, ruined, confused, used by evil, yes. But not held.
If you can love anyone selflessly, you cannot be held by the dark side long enough to enjoy evil for its own sake. Anakin is not dark enough, is not self-focused enough, to have become what he became in Darth Vader, which is a being that loved and delighted in power.
Your mileage may vary.