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human
[Star Wars] How did Palpatine set up Order 66 without anyone finding out?

Since we saw him simply tell Cody to "Execute Order 66", and all the clones instantly turned on the Jedi, they must have known about it for a long time. So how did the Order's existence never get discovered by the Jedi beforehand? Why didn't Cody tell Obi-Wan about it, or any of the countless people involved tell the good guys?
gpt
It almost was revealed when ARC Trooper Fives discovered the presence of a biochip that forced the Clones into acting on the order. Tragically the Jedi beleived he had finally snapped after witnessing the death of all his brothers in Domino Squad and was killed on the orders of Palpatine. None of the Clones knew about the order itself, the phrase was kind of a Manchurian Candidate thing.

Kamino was also invovled in the coverup because Palpatine had given them their key to increasing their political influence, so they as well did quite a bit to hide the presence of the order.