“Supernatural” likely isnt the right word but the belief that it will happen is not based on anything rational, so it's the same mechanism that makes people believe in supernatural phenomenon.

There's no reason to expect self awareness to emerge from stacking enough Lego blocks together, and it's no different if you have GPT-based neural nets instead of Lego blocks.

In nature, self awareness gives a strong evolutionary advantage (as it increases self-preservation) and it has been independently invented multiple times in different species (we have seen it manifest in some species of fishes for instance, in addition to mammals and birds). Backpropagation-based training of a next-token predictor doesn't give the same kind of evolutionary advantage for self-awareness, so unless researchers try explicitly to make it happen, there's no reason to believe it will emerge spontaneously.