Washington Post columnist Ezra Klein, or rather Internet commenter Paul Alexander’s channeling of him, has the answer:
Well, he was about 8 feet tall with really big fangs. This one time him and his buddies flew a rocket ship into the Freedom Building in New York City and killed 6 million people. It was called the Holocost at 9/11 Street. He survived, though, and flew back to Afghaniraqovia on a magic carpet. He then set to building a gigantic army of evil which consisted of every man, woman and child of Arab descent. He used mind control like Dr. Mabuse. I think everyone was, and understandably so, convinced that he could only be killed with Excalibur. And when I asked Wally down at the yogurt shop what he thought about his death, he shrugged his shoulders and asked, “Do you want Oreo cookie bites on this like usual?” I lost it right there and started screaming and yelling and asking if he cared about anything in this world. I think I had a right!
I’d only add that Osama was also the guy who stole Christmas that one time.