A jedi once asked me, "If I have a animal with four legs and a tail, andwe decide to call the tail a leg. How many legs does the animal have?"

I answered, "Five legs?"

The jedi shook his head and said, "No, it only has four legs. Just because we call it a leg, doesn't make it a leg."
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This is why the jedi lost, and died. They thought that just because Palpatine was called a "republican", "good guy", and "the chancellor" doesn't make him those things.

The jedi took the easy way out, and forgot all of their lessons. They thought that because he had control of te galaxy all ready, it couldn't be him.

For thirty years the jedi had been fooled and played with, and it took their death and the rise of a dictatorship for them to finally see it. They didn't die because they hadn't thought the clones would betray them, they weren't killed by sith. They were slayed by themselves, they'd already lost the minute Anakin joined the order and Palpatine became chancellor.