Throughout Star Wars, many factors pushed Anakin's descent to the Dark Side, but his attachment to Padme was the biggest cause. The Jedi knew the problems that attachment could cause him, so Anakin kept his relationship a secret from everyone, including his master. Yet, it's heavily implied that Obi-Wan knew about his hidden marriage, which makes one wonder why didn't he confront Anakin about it.
Obi-Wan first noticed Anakin's feelings for Padme during the opening of Star Wars: Attack of the Clones. Anakin is nervous and sweating just before they meet her, already showing more emotion than the Jedi are expected to have. He even desperately wants to save Padme during the Battle of Geonosis, to the point where Obi-Wan has to stop him from abandoning their chase for Count Dooku.
Throughout Star Wars: The Clone Wars, Anakin and Padme did a good job at hiding their marriage, but those closest to Anakin still had suspicions. During the final season, it's even revealed that Captain Rex knew all about it and helped Anakin remain hidden while he called Padme. Finally, during Star Wars: Revenge of the Sith, Obi-Wan heads straight to Padme after finding out about Anakin's turn to the Dark Side. He's immediately able to guess that she's pregnant with Anakin's child and finally gets confirmation of the relationship. But by then, it's too late, as Obi-Wan completely missed the opportunity to sit and talk with Anakin about his secret.
With relationships forbidden by the Jedi Order, Obi-Wan knew that Anakin would get in trouble if the Council found out, making him not want to speak about it out loud. Unfortunately, that only encouraged Anakin to keep his secrecy, and in doing so, he started to feel that the Jedi weren't people he could trust. But what Anakin really needed was someone in the Jedi Order who could help calm stay him after he started seeing visions of Padme dying.
Obi-Wan could've understood Anakin's attachment, as The Clone Wars revealed that even he once had a relationship. Before Star Wars: The Phantom Menace, a young Obi-Wan and Qui-Gon Jinn were sent on a mission to Mandalore. During this time, Obi-Wan grew close to Satine Kryze, a duchess who eventually became the leader of Mandalore. Ultimately, he knew that he had to choose Satine or the Jedi, so he eventually left her. But upon reuniting years later, Obi-Wan explained that, if she had asked, he would've dropped the Order for her. Anakin even gathered that the two had a history, yet once again, Obi-Wan refused to talk about it. It would've been the perfect time for Obi-Wan to explain the issue with Jedi having a relationship, but his reluctance to talk about personal issues got in the way.
The Jedi had many flaws during the prequel era, and they all led to Anakin distrusting them. Even Obi-Wan, who was one of the more ideal Jedi Masters, couldn't confront Anakin's emotional problems, instead choosing to sweep them under the rug. If Obi-Wan had been more open with Anakin about his relationship, the young Jedi would've trusted more in his teachings and Anakin wouldn't have felt the need to turn to Palpatine, who was the only person that would listen to him.