I seem to remember us becoming embroiled in another conflict that was no concern of ours, based on "absolute proof" that WMDs existed.
No, pdq, politicians don't learn. They continually make mistakes which their experience should tell them not to make and which, if made in the commercial world, would cost them their jobs and more. They always know best; they often disbelieve what they are told; they often make crass decisions which fly in the face of common sense. For the electorate's part their opinions are usually ignored; they always think the latest bunch of politicians cannot possibly be any worse than the last lot; they are always wrong.