If it's basic math, how come China and India haven't ruled the world forever, since they have the largest populations? There's a lot more to it than what you say.
And even that dominance is thanks almost entirely to the Islamic golden age that preceded it.
And just like the ignorant muslim empires in 1200 who assumed they would rule the world forever, Westerners haven't realized the rest of the world has caught up to them and the European age is over.