From scratch in the sense that it starts with random weights, and then experiences the world and builds a model of it through the medium of human text. That's because text is computationally tractable for now, and has produced really impressive results. There's no inherent need for text to be used though, similar models have been trained on time series data, and it will soon be feasible to hook up one of these models to a webcam and a body and let it experience the world on its own. No human intelligence required.

Also, your point is kind of silly. Human children learn language from older humans, and that process has been recursively happening for billions of years, all the way through the first forms of life. Do children not have intelligence? Or are you positing some magic moment in human evolution where intelligence just descended from the heavens and blessed us with it?

Just like humans are! Do you know what happens when a human grows up without any training by other humans? They are essentially feral, unable to communicate, maybe even unable to think the way we do.