I think there are a few factors you can look at. The easiest ones to look at are Anakin and Obi-Wan’s faults. Obi-Wan did not train Anakin well, a fact he admits in ROTJ, and Anakin was selfish. Obi-Wan was very hard on Anakin, to the point where it seemed absurd (to me, at least) while watching AOTC. That said, I think there's a more important factor. It's not spelled out in the films, and it's more philosophical, but it speaks to the ultimate catalyst for why Anakin fell to the dark side: Padme. Not that she herself was to blame. That’s not what I mean at all. When I say Padme, I mean his love for Padme and his loyalty to the Jedi Order. Palpatine played on the fact that Anakin had to keep his marriage a secret. The only guidance Anakin could seek was from Yoda, where he got vague guidance because he told Yoda a vague problem, and from Palpatine. Anakin’s central conflict, therefore, was between love and duty. I’m of the opinion that Anakin did not need to have that conflict. So what is at fault? The Jedi Code. The Jedi Code speaks to the idea that a Jedi shall not know love. It forbids love, and it forbids romance, quite unnecessarily in my opinion. In the words of Jolee Bindo from Knights of the Old Republic, “Love doesn't lead to the dark side. Passion can lead to rage and fear, and can be controlled... but passion is not the same thing as love. Controlling your passions while being in love... that's what they should teach you to beware. But love itself will save you... not condemn you.” That was a fact lost on the Jedi Order. According to Anakin, the Jedi forbid attachment and possession and only allowed compassion, which left no room for romance. Only romance, as Jolee rightly said, won’t destroy you. What Anakin needed to be taught was how to control his passion in his romance and how to control his fears about his dreams (dreams that became a self-fulfilling prophecy). Only he couldn’t seek out that guidance. If he had, he would’ve had to admit his romance and marriage to Padme. If he had, he would’ve been expelled from the Jedi Order. He had nowhere to turn to but Palpatine, because Palpatine was the one who gave Anakin the sense of "I understand." Because of that, once Palpatine hooked him, Anakin was in a position to believe that the Jedi stood opposed to him. That's where the friendship between Obi-Wan and Anakin finally broke down. Obi-Wan represented the Jedi, and, to Anakin, the Jedi were the ones ruining his life. In a way, he wasn't wrong.