1. Content of the message (GOSPEL-CENTERED DOCTRINE) The Apostles were veracious cross-clingers. No amount of cultural pressure could hide their clear and compelling attachment to the work of Jesus, both his crucifixion and resurrection. So when they spoke, there was not even the slightest attempt to make what had just happened -- the Gospel -- palatable or polite. The Gospel is where they started, stayed, and ended. And everything else was built on that.
2. Character of the leaders (SHEPHERD-LIKE AUTHORITY) Speaking truthfully, living authentically, witnessing boldly, enduring faithfully, giving selflessly ... these were the traits of the leaders. They were the ones who first modeled what God showed us in Jesus -- sacrificial leadership! They cared and they shared. It only makes sense, then, that the rest of assembly, for the most part, followed suit.