He was black and had a foreign sounding name. That's really it. It's why he also got the Nobel Peace Prize immediately after getting elected.
One must not underestimate the power of white guilt. America is still largely controlled and populated by white people and there is nothing most white people want more than to have everyone like them for some reason. White people are desperate to be accepted and liked by black people especially so they elected a young black man with a muslim sounding name and were genuinely excited by the prospect.
Young people will struggle to believe the stories of the fever that enraptured the whole fucking country during that time. For the first time in my life, for 8 years nobody made fun of the president. I can't recall any comedian other than fringe Conservatives who made fun of him in the mainstream, for anything. No musicians took on the president (except a couple, like Lupe Fiasco.) No movies. No media saying things like "controversial in the Obama Era..." They made mainstream cartoons mocking George W and Trump, but not Obama. Never Obama. I remember a whole cottage industry popping up of people calling George W a goofy exceptional individual who looked like a monkey. But of you say Obama talks funny, you're a bigot. Every magazine sucked his dick. Greatest president of all time. "We should elect him as president forever!"
Why?
Because he was a young black man with a muslim sounding name and white people were and still are desperate to be loved by everyone. If you are any black woman in America, you can hold a microphone and immediately get 10,000 white women listening to you. This is why everyone thinks white people are goofballs but... Nothing changes. Vote Oprah.