Many beliefs also include legends of people dying and becoming a God or Goddess. Without intending to denigrate any honestly held beliefs of anyone out there, it is all too obvious, if you study the vast range of human religious belief throughout history, that mankind actually creates God in the image of man, NOT the other way around. This added the idea that the actions of God must be controlled according to some overarching moral code. Christianity has struggled with all of the various implications of that question throughout its existence. Still to this day, there are sects of Christianity which believe in predestination and sects which do not.
Predestination is unworkable as an answer for oh so many reasons.
And yet, you cannot ignore the fact that many people have some ability to foretell the future. Clearly, Spengler had that ability. This is not foretelling the future, but is instead just the result of keen powers of observation, analysis, and conclusion. It only really matters that someone is there to perform the necessary task to move on to the next stage of development. On the other hand, Napoleon lost the battle of Waterloo, and was imprisoned the rest of his life.