Dumbledore is a lot better than Snape, but on the other hand he does some pretty dumb things too. The main one being his problem with never telling anyone anything. I just finished rereading book 5 and it's pretty ridiculous his secrecy was. I mean he KNOWS that Harry is destined to fight Voldemort to the death, and he KNOWS that Voldemort wants to use Harry to get the prophecy, yet he tells Harry absolutely nothing, for no good reason.
I mean, he said that he didn't want to burden Harry with knowing about the prophecy. But how about telling Harry why he needs Occlumency? If he had just said one thing about the possibility of Voldemort planting false images in his head, maybe Harry wouldn't have been tricked. Or he could have told Harry why he wasn't talking to him. Or given Harry a way to contact him in case of emergency. I dunno, it just seems kinda dumb that Voldemort's plan worked - it never would have worked if Harry had been reasonably informed.
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I made a living on time trial blowing myself off to cross the finish line at ludicrous speed. -transience