So I feel like if Obi Wan was to fall to the dark side it would probably have had to due with Count Dooku. So in the Attack of the Clones movie Count Dooku tries to get him to join him when during this conversation.
"Count Dooku: What if I told you that the Republic was now under the control of a Dark Lord of the Sith?
Obi-Wan: No, that's not possible. The Jedi would sense it.
Count Dooku: The dark side has clouded their vision. Hundreds of senators are now under the influence of a Sith Lord called Darth Sidious."
If Obi Wan had believed Count Dooku here and decide to join him because the Sith controlled the Republic I believe that over time Dooku would have corrupted Obi Wan to the dark side. If this had happened it would have had some interesting ramifications. Seeing as Obi Wan was consider on par with Yoda and Mace for knowledge of the force and skill with a light saber respectively, it would be safe to assume that a less skilled Jedi would probably have lost the battle against General Grievous. This would have meant that whoever was sent to Utapau would probably have died and also Count Dooku + Obi Wan would have defeated Anakin when they invade his ship during the battle of Coruscant. Also at this point Obi Wan might have been able to convince Anakin to switch sides there or even before there. If this happened the balance would have heavily swayed in the war.
So the next question is how would Sidious react to these changes. Would he continue orchestrating the down fall of the Separatist movement or would he try a new approach of have the Separatist defeat the republic and then install himself as the lead or the shadow lead of the new government the Separatist impose. Each of these would be an interesting story.
Written 23 Nov 2015 •