His turn wasn't at all abrupt. Anakin was brought into the Jedi Order too old for his age in Phantom Menace. This was the Jedi Council's first concern, but they only brought him in because they saw him as the chosen one that'll bring balance. In truth, they wanted to use Anakin for their own selfish purposes just as much as Palpatine. But where Palpatine went out his way to befriend Anakin, the Jedi went out their to undermine him. And that's been one of the things that was bubbling over within Anakin. Anakin was already bubbling with a lot of emotion to which the golden rule is to shun all emotion. So, in Episode 2, Anakin is supposed to behave devoid of emotion, but it was an impossible task when he have fallen fully in love with Padme and found his own mother dead and that hidden rage exploded foreshadowing what he was to come. He kept all of that a secret from the Jedi order. In Episode 3, he became a Jedi Master and was viewed as one of the best to master the art of being a Jedi, yet the Jedi council STILL undermined him which he expressed his frustration to Obi Wan. Then learning about Padme becoming pregnant and his dream of her dying, got his emotions all riled up again because of what happened to his mother and the vision he had and his inability to prevent it. He first went to Yoda for advice and Yoda gave him some bullshyt of just push your emotions away, and that's where he went to Palpatine who been nurturing him to lean more to the darkside. So the turn wasn't never abrupt. He was fighting it the entire time, especially in episode three. Every time he asked or propose something to the Jedi it gets undermined and Anakin gets dismissed. The final last grasp was when he learned that Palpatine was a sith and he tried to do the right thing by reporting it, but first Mace Windu ordered him no when Anakin offered to come with him, saying that he senses confusion and to wait at the Jedi Council. Anakin actual turn happened while at waiting at the Jedi Council. This was the point of no return....
By that point he's willing to do anything. And once Mace realizes that he have to kill Palpatine which Anakin correctly states is not the Jedi way, and Mace essentially paraphrased "fukk the Jedi way, this muthafukka needs to die"......Anakin did what he did... he was already in debt to Palpatine.
The problem isn't the story or acts in the story.... it is the dialogue itself.