Alexander the Great was drinking too much, he kept forgetting what Aristotle said about the histories of Darias and Xerxes being facts not fiction, and his armies and their translators (not like Ptolemy and the Jews in Egypt) were seduced by the Persians they were conquering. And that is why the Roman empire could exist. It had no serious something to deal with.
Fine - you say I'm conjecturing a bit. And I say Jim O'Donnell is too. (HT Mark Liberman)