Colin Powell's endorsement of Obama

There should be little surprise that Powell endorsed Obama. Powell had a long and distinguished career as a public servant, but this career contained one embarrassing blotch on it. When he was secretary of state just before the Iraq invasion, he came before the United Nations and gave a speech describing the efforts to produce weapons of mass destruction in Iraq. He was putting his great personal prestige behind the Bush administration's justification for starting a pre-emptive war.
The only problem was that the facts he quoted in the speech were lies, fabrications. They were fabrications by Iraqi expatriats, opponents of Hussein, who hoped that they would become the new leaders of the country with Bush's help. They concocted a fancy tale of chemical weapons being created in mobile labs semi-truck trailers. They concocted links between ben Laden and Sadam Hussein. They created tales of attempts to purchase uranium in Africa. Now, expert weapons inspectors from the United Nations had been trying to find weapons of mass destruction for months but had failed. This did not matter to the Bush and Cheney and their neo-conservatives who did not trust the UN anyway. In their defense, our intelligence community had very few "on the ground" operatives in Iraq. A previous administration had ended this work, believing that electronic survelience and satelites were enough.
Bush and his friends, on a mission to protect and spread democracy (and to protect our oil supply and companies), were ready to believe any wild thing they heard about Iraq and they disregarded CIA and other warnings that they should not trust these ambitious expatriats. Bush and friends convinced Colin Powell that the evidence was overwhelming and he should make his speech. That speech was perhaps the most convincing part of Bush's propaganda campaign to promote his war. Why did Powell endorse Obama?