The Administration knew, even Trump seems to have known, that they could not get away with a straightforward Muslim ban.  Thus Giuliani was tasked with formulating an order that would accomplish the goal of banning Muslims, but in a way that would pass muster in court.  We're in the process of discovering how the courts will find on this.  The ban works this way: Everyone from the named countries is banned; then a class of exceptions is created for Christians, thus effectively banning Muslims.