I actually forgot about the few captains who did see through it: that's a very valid point. I'm not too quick to defend old man Yama, but I don't think it comes down to a matter of intelligence as much as the chain of command. Yama follows the orders of Central 46, at least in matters such as Rukia's predicament. He may not like it, but his responsibility is to enforce it. He may very well make inquiries, or question Central 46 on their decision, but he wouldn't do it openly. You should also consider that, perhaps, Yama has been more of a target for Aizen's powers since he is in a position of power. Why would Aizen go after one of the other captains directly, unless they got in his way? Finally, I should mention that the other captains interfering may very well have been part of his plans.Originally Posted by Kraco
As for the disparity of sentences, both sentences served Aizen well. Aizen wouldn't want Kisuke dead, once he knew Kisuke was conduction holofication research, and Aizen wanted Rukia burned to a char, since there was no risk in that method to losing the square shiny, willful holofication thingamajig.
I think people are underestimating the power of Aizen's zanpaktou. Another possibility is that Yama is actually working for Aizen, as crazy as that may seem. I mean, the mans old as dirt and still hasn't been promoted to king's guard. He could hold a grudge, I suppose.