Megan Crouse writing at StarWars.com:
As heroes of the Clone Wars, Obi-Wan and Anakin suffered not just the tragedy of their duel during the fall of the Republic, but also the aftermath, almost two decades of living on opposite sides of the galaxy-spanning war. So much has been written about them before, and about how Palpatine slowly and subtly chipped away at Anakin’s trust in the Jedi in general and Obi-Wan in particular.
The relationship between Anakin and Obi-Wan is one of the great tragedies in the Star Wars universe. This article does a great job of exploring how that deteriorated over time and how Palpatine exploited it.