It's kind of debatable if the reasons were "sound". The only reason was that Palpatine expressed a "bond" with Anakin and would probably be agreeable if it was him they chose to guard him. Which is one sound reason, but not much else. I will 100% agree with you that it was a gamble on their part that failed. You're right.
The mods have also said the EU is not to be labored on as being somehow definitive. This is a "Star Wars Prequel Movies" forum. I am allowed to answer questions purely from a movies point of view. All I said was "Ignoring the nonsense that is the EU." That does not even remotely qualify as "bashing" and there is no forum rule that says everyone has to love the EU. If you don't like it, please feel free to place me in your ignore file.
No one is laboring on it as being definitive. Calling the EU nonsense is bashing. If you have your own opinion on a subject, feel free to say it. There's no need to take cheap potshots at the EU every time it is mentioned here.
Well, that's just the point: Palpatine had a close relationship with Anakin that he simply didn't have with any other Jedi. That sort of unparalleled access is what a successful spy would need. Anakin was the only viable option. Yep. But, really, the Jedi weren't too far off the mark: Anakin's allegiance to the Order did outweigh his personal loyalty to Palpatine, which is why he reported the Chancellor's duplicity to Mace. The spanner in the works was that Anakin's devotion to Padme exceeded his dedication to either the Jedi or the Chancellor. Palpatine knew that and exploited it. It was a risky gambit, but the Jedi had sound reasons for playing Anakin against Palpatine and it initially succeeded... until Palpatine used his trump card: Padme.
It would be hard for him not to know as at the end of AOTC they are in each others presence physically,It is not like Sidious's interaction with say Ventress in the EU where all she sees is a hologram.
The novelization as well as what Lucas himself said. "Palpatine has told Dooku. 'I have somebody who I think will be a great Sith Lord and I think we can get him to join us. But we need to test him. So we're going to setup a situation where you fight him. If he gets the best of you, then I'll stop the fight and he'll have passed the test. If you get the best of him, then we'll let him go, and we'll let him stew for a few more years until he's ready.' But behind it, obviously, is Palpatine's real intention: If Anakin is good enough, Anakin can kill Dooku and become Palpatine's new apprentice. But he didn't tell Dooku that." --George Lucas, The Making Of ROTS; Page 41.
The only problem with that is it ruins whatever minor surprise would be had when Anakin says "You're the Sith Lord!" Not that everyone wasn't expecting it, but that's probably why Lucas didn't put it in the movie.
But the book said he was still cuffed to his chair, so that would've given it away outright...again, as if everyone weren't expecting it. Really, it was given away outright when Palpatine swiveled around in his chair in that homage to ROTJ.
The scene would give away more than Palpatine being Sidious, it would give away that Dooku was going to be betrayed by Palpatine.
Narcissism is something of a darksider trait - Dooku figured that he was worth enough to Palpatine that he would never be "thrown away".
There was that great moment in the ROTS novelization where Dooku's final thought as he realized that Palpatine had betrayed him: Treachery is the way of the Sith. 20/20 hindsight defined.
Yup - both before he loses the duel, and after: Dooku allowed himself to relax; he felt that spirit of playfulness coming over him again as he and Skywalker spun 'round each other in their lethal dance. Whatever fun was to be had, he should enjoy while he could. Then Sidious, for some reason, decided to intervene. "Don't fear what you're feeling, Anakin, use it!" he barked in Palpatine's voice. "Call upon your fury. Focus it, and he cannot stand against you. Rage is your weapon. Strike now! Strike! Kill him!" Dooku thought blankly, Kill me? He and Skywalker paused for one single, final instant, blades locked together, staring at each other past a sizzling cross of scarlet against blue, and in that instant Dooku found himself wondering in bewildered astonishment if Sidious had suddenly lost his mind. Didn't he understand the advice he'd just given? Whose side was he on, anyway? And through the cross of their blades he saw in Skywalker's eyes the promise of hell, and he felt a sickening presentiment that he already knew the answer to that question. Treachery is the way of the Sith. ... "Anakin," Palpatine says quietly. "Finish him." Years of Jedi training make Anakin hesitate; he looks down upon Dooku and sees not a Lord of the Sith but a beaten, broken, cringing old man. "I shouldn't—" But when Palpatine barks, "Do it! Now!" Anakin realizes that this isn't actually an order. That it is, in fact, nothing more than what he's been waiting for his whole life. Permission. And Dooku— As he looks up into the eyes of Anakin Skywalker for the final time, Count Dooku knows that he has been deceived not just today, but for many, many years. That he has never been the true apprentice. That he has never been the heir to the power of the Sith. He has been only a tool. His whole life—all his victories, all his struggles, all his heritage, all his principles and his sacrifices, everything he's done, everything he owns, everything he's been, all his dreams and grand vision for the future Empire and the Army of Sith—have been only a pathetic sham, because all of them, all of him, add up only to this. He has existed only for this. This. To be the victim of Anakin Skywalker's first cold-blooded murder. First but not, he knows, the last. Then the blades crossed at his throat uncross like scissors. Snip. And all of him becomes nothing at all.