He was Iranian Shah, and big friend of USA. It was USA, who assisted in building research center, supplied equipment and enriched uranium for experiments. Germany begun building of Busher nuclear power station, because West persuaded Pekhlevi to use nuke energy instead of oil and gas. At that time there where no Islamic states led by mullahs, nobody even can imagine about such thing. And nobody would believe in crushing of USSR and Warsaw Treaty.
That's just it. You don't know what will happen 50 years later. You have to assist your allies in the present, you don't have the luxury of cutting them off on the assumption that they will be your enemy via a coup or revolution or whatever a half-century later.
Maybe England and Taiwan will be our mortal enemies in 2056. But should we treat them as such now?