Who was doing exactly what they suspected him (or one of his inner circle) of doing but didn't have the proof.
He uses Anakin's wife to get to Mustafar, and does nothing to correct the impression that she knowingly betrayed her husband. And he did go there to kill him.
What good would it have done for Obi-wan to defend Padme? Anakin wouldn't have believed him anyway. It would have made it even worse.
When Skywalker went to Yoda for advice, all he got was Jedi bromides about detachment, etc.
And all we get from Anakin is his crazy desire to make sure no one ever dies and he's willing to do anything to get that power. What Anakin really loved was power, not Padme, not Obi-wan, not anyone else. He didn't love Padme, he was obsessed with her. He killed little children to get the power he wanted over her and over everyone else.
It wasn't until he had to spend twenty years in a walking iron lung that he realized that power was a cold mistress.
And let's not forget that the Jedi Council initially didn't want Kenobi to take him on as a Padawan - because he was too old, i.e had developed family attachments.
Yeah, we also know how much Palpatine valued "family attachments".