I think what's happening here is the conflation of a seed and a plant, or an egg with a chicken.

Everything in the universal contains potentialities. A thing has the potential within it to become other things, as a seed could become a plant (or be an ingredient in a meal).

So what you're seeing here is that. The capacity for capitalism exists within certain dynamics. The seeds of capitalism existed within the feudal system, for instance, and they matured through the adolescence of mercantilism. This was a potential which was unleashed through historical events like the Bubonic Plague and technologies like the steel plow or steam engine or ideologies like the Enlightenment. Historical events seemed to predetermine a capitalist system, which is pretty much what Marx and Engels argued.

But other potentialities also existed, and still exist. What could mature into capitalism could mature also into something else. Humanity is roughly 100,000 years old and capitalism makes up about 300 of those years. It doesn't look like it's going to make it much longer than that either due to its unstable nature. So it could be that capitalism is just a potential, a very rare potential, for human populations. The conditions were met, and opposing forces were incapable of stopping it (they certainly tried), and so we get it for a short time. But it's not inevitable, and it's not permanent. It just seems like that because it's the globally dominant system and has been for some time now, and that makes it hard to imagine that the world was or could be any other way.