A rare opportunity to switch sides, Obi-Wan stays true to his fatih. Why didn’t Obi-Wan join Count Dooku?
Obi-Wan didn’t join Count Dooku because he didn’t trust him. Dooku has been working secret deals behind the Jedi Council’s back, building a droid army, and coordinating the assassination attempts on Padme.
Dooku suggests that Qui-Gon would have sided with him, but Obi-Wan vehemently disagrees.
Obi-Wan is captured and questioned on Geonosis
In Star Wars: Episode II – Attack of the Clones, Obi-Wan has been captured by Count Dooku. He discovers a Seperatist meeting coordinated by Dooku. Suspended within a holding device, Obi-Wan awaits to be approached and informed of next steps.
As Count Dooku approaches, Obi-Wan calls him a traitor. Dooku disagrees, saying Obi-Wan’s capture has been a mistake.
Curious that Obi-Wan is on to his plan, Dooku asks why a Jedi Knight is all the way out on Geonosis. Obi-Wan says he’s been tracking a bounty hunter named Jango Fett. By using a device, Obi-Wan has been able to track Jango Fett through hyperspace.
Dooku attempts to deflect by saying no bounty hunters exist on Geonosis, as the Genosians don’t trust them. He then states that it’s a pity Obi-Wan’s path has not crossed his own before.
Obi-Wan refuses to join Count Dooku
Qui-Gon, Obi-Wan’s master, spoke very highly of him, according to Dooku. The Count says he wishes Qui-Gon was still alive, as he can use his help right now.
Obi-Wan sternly states that Qui-Gon would never help. Dooku says not to be so sure, as Qui-Gon was once his apprentice. He says that Qui-Gon knew all about the corruption in the senate, but he never would have gone along with it if he had learned the “truth” as Dooku has.
Dooku informs Obi-Wan that the Republic is now under the control of the Dark Lord of the Sith. In denial, Obi-Wan says the Jedi Council would be aware of it. Dooku retorts, saying the dark side of the Force clouds their vision.
Hundreds of senators are now under the influence of a Sith Lord called Darth Sidious, according to Dooku. The Viceroy of the Trade Federation, who previously attempts to end Obi-Wan and Qui-Gon with toxic gas, was once in league with Darth Sidious.
The Viceroy was betrayed ten years ago by the Dark Lord, according to Dooku. He comes to Dooku for help and exposes everything. At that moment, Dooku asks Obi-Wan to join him. Together, Dooku says, they’ll destroy the Sith.
Obi-Wan says he will never join Dooku. Disappointed, Dooku leaves the room and suggests that securing Obi-Wan’s release will be difficult.
So that’s the answer. Obi-Wan didn’t join Count Dooku because he didn’t trust him. Dooku has been working behind the Jedi Council’s back to build a droid army and assassinate Senator Padme.