It is easy to understand how it began, because of course, some things, like the seasons the tides and the breeding cycles of many animals, are in fact, predictable by observing the movements in the sky. And in ancient times, when most people lived by primitive agriculture and/or hunter gathering, those sorts of things and predicting them, would have been really important, in a way that we can hardly understand now. While the movements of the planets and stars, were one of the few entertainments available while you sat round the campfire at night.

So that it was only a small jump of false logic to start thinking. If the big really important things follow the movements of the stars, perhaps the little things do too.