This is mainly because Wes had a good relationship with harden in the past, and was a teammate during the thunder period. However, Wes played in the Rockets in the past season. Wes was very dissatisfied with his lack of ball power and tactical position. He didnt want to play with harden again, so he decided to leave here.
According to the current news, harden learned that he would rather join hands with wall than continue to play with wes. In the off-season this year, Haden also trained and played with players like wall, and now the deal meets his requirements.