Asimov is Mr. Science Fiction. He might not have created the genre, but he sure helped create it as we know and love it today. Foundation, yeah, it's all about science fiction too. It takes the idea of a collapsing empire—like the historic Roman Empire—and throws it into space. Chariots become spaceships; territories, planets; and soldiers carry ray guns, not gladii.
So, why science fiction? Two reasons. First, he gets to rewrite history as the future, and who wouldn't want to do that? Second, he can comment on modern society by drawing parallels between Foundation's future society and our own.
Foundation is also a war drama…of a sort. Most war dramas take place in an actual war. All Quiet on the Western Front, For Whom the Bell Tolls, Slaughter-house Five: these are all examples of war dramas. In Foundation, war always looms as an inevitable threat and preventing it becomes the main motivation of both Hardin and Mallow. But there's never an actual war in Foundation. In a way, Asimov's anti-war message makes Foundation an anti-war drama too.