The snag was that if he told all he knew, people would discover that he was not truly human. We are like that family of aliens, strangers in a strange land. We know things others don't know. We experience life differently. And sometimes it's dangerous for others to find out our true loyalties.
Christians are aliens.
We live in a country to which we are loyal, of course, but we know that our true home, our true sovereign is somewhere else. Such a concept would have been especially meaningful to a Philippian citizen. Their city, Philippi, was a Roman colony way out on the frontier. Yet they held citizenship in the far off city of Rome. If there was trouble, they would look to Rome to save then, protect them.