Theodore Roosevelt had blood ties with the Belmont Clan.That's why Death had to take him while sleeping, for if Roosevelt had been awake, Death would've lost.
Theodore Roosevelt was God's prototype for Chuck Norris.When the Lord saw the power of His creation, He knew that He could not let it end there. So He spent years, trying out just the right combinations of Awesome and Cool, until He finally gave us the Texas Ranger himself.
Theodore Roosevelt is either God, or at the very least a god.Extremely charismatic? Check. Ridiculously larger-than-life figure? Check. So badass as to be borderline unbelievable? Check. Possibly immortal? Double check. Really, I'd be more surprised if this wasn't true.
Theodore Roosevelt is still alive.Death was merely able to knock him unconscious for a while. TR slumbers underneath Mount Rushmore with the Rough Riders and shall awaken to save America in its hour of need.
Theodore Roosevelt was actually an identity of the God-Emperor of Mankind.Search your feelings, you know it to be true.
Theodore Roosevelt was one of the Unknown Primarchs
Theodore Roosevelt was a Khornate
Theodore Roosevelt died because he wanted to.Let's be serious here, he could've kicked Death's ass in his sleep. The only reason he died was because he was bored with this world and wanted to see the afterlife (and pwn it), so he went without a fight (in his sleep because Death would've been too afraid to show up if he was awake).
Theodore Roosevelt gave his infamous Big Stick to America.Remember that strip with Canada where he had a big stick lying around? That used to be Teddy's. Since he couldn't trust it to mere humans, he decided to give it to the only one he saw worthy of it: Alfred Jones/America. And it wouldn't it be surprising if some of his enthusiasm rubbed off on the Nation.
Theodore Roosevelt was a scion of The Erlking.Think about it. He loved hunting, was a total badass, and really only cared about conservation so he would always have something to kill. It's either that, or he was like the Summer/Winter Knights, except for The Wild Hunt.
Theodore Roosevelt isn't in heaven.Two reasons: One: to put the fear of GOD back in Lucifer. Two: God himself worries over his position while the man is around.
Theodore Roosevelt wasn't taken in his sleep.It was a trap for Death. He was waiting for Death and is now in the afterlife hunting the bastard for taking his family members from him.
Theodore Roosevelt was our world's embodiment of Spiral Energy.Every reality/world/universe has one. So now the Guessing must be on WHO REPLACED HIM!
If the Earth is ever invaded by aliens, the US government's secret contingency plan is to awaken Teddy Roosevelt
He'll come back as a White LanternAnd he'll light our darkest hour Grim Reaper.
With a couple centuries, Theodore Roosevelt will be viewed as the American King ArthurHe's already approaching that status now. Just imagine three hundred years down the road when history has been sufficiently distorted to the point that he'll become a literal legend, where no one knows what's true and what isn't. Reincarnation legends are going to be everywhere.
World War I was a complicated assassination of Theodore Roosevelt.As mentioned, the only reason that Roosevelt died was because his son Quentin was killed in World War I, resulting in Death by Despair. A group of time travellers, or one of the Powers That Be was rightfully paranoid that they would have to confront Roosevelt, so they set the events of World War I in motion. The first plan was the aforementioned Death by Despair-while also Badass, the son was not as badass as his father, and thus could be killed in the horrors and sheer magnitude that it turned out to be. The second was, if that didn't happen, to lead to World War II, which would result in the development of the nuclear bomb. They figured that if Roosevelt could be killed, a city-obliterating weapon would do the job. As for the most likely culprit? The Nazis. Without the World Wars sending Germany into poverty, not only would Theodore Roosevelt pester them, but they'd be stuck as a minor political party no-one cares about. One could argue that they still got dealt the losing hand, as they ended up becoming the most hated group on the planet(though unlike the Westboro Baptist Church, they're still cool.)
The universe will end when Theodore Roosevelt and Rory Williams meet.