The deepest difference between religions is not that between polytheism and monotheism.
The only theism worthy of our respect believes in God not because of the way the world is made but in spite of that. The only theism that is no less profound than the Buddha's atheism is that represented in the Bible by Job and Jeremiah.
It is widely assumed, contrary to fact, that theism necessarily involves the two assumptions which cannot be squared with the existence of so much suffering, and that therefore, per impossibile, they simply have to be squared with the existence of all this suffering, somehow.
Thirdly, even if we assume that the world is governed by purpose, we need only add that this purpose - or, if there are several, at least one of them - is not especially intent on preventing suffering, whether it is indifferent to suffering or actually rejoices in it.
The doctrine of original sin claims that all men sinned in Adam; but whether they did or whether it is merely a fact that all men sin does not basically affect the problem of suffering.
Here an attempt is made to explain suffering: the outcaste of traditional Hinduism is held to deserve his fetched fate; it is a punishment for the wrongs he did in a previous life.