He’s the only one because he’s still around. If he died yesterday we’d have someone new leading the charge by election time.
You’ve specifically pointed out ideologies that weren’t allowed to die because of how oppressed they were. I’m not suggesting we shouldn’t have fought the Nazis, but victory inherently creates an oppressed underdog that people love to rally around.
The ideologies that die are the ones that fail on their own and people lose faith in. Think monarchies, feudalism, mercantilism, the OG version of Communism, colonialism, etc… So ideally we won’t want to use force if at all possible. Let them lose election after election until they realize they’ve alienated too many people to ever be successful.