Fukuyama is best known for writing "The End of History" which theorized that, after the end of the Cold War, western liberal democracy was pretty much "it" and we were essentially just playing cleanup. There would be no more real challenges to that status quo, just further development of it.
It's still entertained in certain circles but things like the current rise of global fascism makes a pretty strong case that history isn't really over and western democracy is just as transient as feudalism or monarchy or any other form of government that was widely adopted.