Anakin Skywalker turns evil primarily due to a combination of personal tragedy, intense emotional struggles, and manipulation by the Sith Lord Palpatine. Key reasons include:

1. The death of his mother, Shmi Skywalker, triggers overwhelming grief and rage in Anakin, leading to his first act of dark side violence when he massacres her captors, the Tusken Raiders.
2. His secret love and marriage to Padmé Amidala, forbidden by the Jedi Code, creates deep fear and anxiety for her safety, especially after visions of her dying in childbirth.
3. Palpatine, secretly the Sith Lord Darth Sidious, exploits Anakin’s fears and ambitions by mentoring him and promising the power to save Padmé, gradually eroding Anakin’s trust in the Jedi Council.
4. Anakin’s growing distrust and alienation from the Jedi Council, feeling undervalued and mistrusted despite his powers, further isolates him.
5. The decisive act of betraying Mace Windu to protect Palpatine, whom Anakin believes holds the ability to save Padmé, seals his commitment to the dark side and solidifies his transformation into Darth Vader.

Ultimately, Anakin's turn is driven by his desire to prevent loss and death, but his fear and emotional vulnerabilities make him susceptible to manipulation and lead him to choose the dark side as a means of control and power to protect his loved ones.