For anyone who still plans to see season five, this thread contains spoilers.
Lets face it. The producers had to find a way to get rid of Ahsoka. She is not in the Original Trilogy, so they needed a way to explain her absence. They really only had two options, either Ahsoka dies or she leaves the Jedi Order. Thankfully they didn't kill her off :D However, the plot they developed and the reasons behind Ahoska deciding to willingly leave the order call for some interesting contemplation.
The movie, Star Wars The Cone Wars (takes place chronologically before season one), provides the story behind Ahsoka being assigned as Anakin's padawan. Though it is said that she was originally meant for Obi-Wan, it is implied that she was intended for Anakin all along.
Consider the position of the Jedi Council. There is strong evidence to support the speculation that Anakin is the chosen one. From the very beginning, they sensed fear in Anakin, and they had much to lose if Anakin turned to the dark side. Can we honestly think that the council would leave anything up to chance with him? I think not. Every single mission and circumstance that Anakin was ever in was organized by the Jedi Council, including his mentorship of Ahsoka. Yoda himself said, in regard to Anakin, "Ready he is to teach an apprentice. To let go of his pupil, a greater challenge it will be. Master this, Skywalker must." He didn't say that Ahsoka would lose Anakin, but the other way around. Ahsoka is obiously younger than Anakin, so logically, Yoda meant that Ahsoka would die.
My theory is that the council purposely planned the extermination of Ahsoka. Ahsoka was a pawn, simply another lesson that Anakin had to be taught (the sense of loss, the pain that emotional attachment can bring). They knew that she was very much like Anakin, and that if she were framed for crimes against the republic, she would stop at nothing to redeem herself. She would try to escape custody, and would eventually be either killed, convicted, or expelled from the order. I would not go as far as to say that the Jedi council pre-planned the bombing of the Jedi temple. But it was the perfect opportunity they had been looking for to get rid of Ahsoka. They purposefully assigned Anakin and Ahoska to investigate the bombing.They manipulated Barriss Offee to bring about their master plan for Anakin. But something happened that they did not expect: Anakin proved Ahsoka's innocence. Just when they thought that their plan had failed, Ahsoka decided to leave the Jedi order. And she was right in her decision. She realized that the council had no trust for its members, so she could not put her faith in them anymore. Throughout season 5, she repeatedly expresses her doubt as to the morality and wisdom of the clone wars. She begins to realize that the council is using her, and she was wise to leave when she did. Too bad that Anakin hadn't realized that the council was also using him. Maybe then he could have avoided the later horrors that came to place in his life. But Ahsoka did not try to convince him. It is implied in the end of the last episode that she knew of Anakin's involvement with Padme. But she also realized that Anakin would have to come to his own conclusions about the Jedi and their purpose
In conclusion, this is purely my speculation :D
Nobody get mad please lol, I like to think of alternate meanings to Star Wars scenarious.
Plus, I am majorly biased towards Ahsoka, since she is my favorite character and I relate to her so much.
It made me so mad when Mace Windu said that Ahsoka's fight for survival and redemption was "actually her Jedi trial". That is complete bull. Excuses. grrrrr :D lol
Finally, any other theories out there?
Any other reasons why the council would so readily accuse one of it's own?
Would love to hear new perspectives!