Why do Protestant Christians accept the Apostles' Testimony as Credible, Reliable, and Substantial for Dedicating their Lives to?

The **Testimony of the Apostles** concerning the ministry, miraculous deeds, and alleged Resurrection, was fantastic, way out of the ordinary, revolutionary, and mind-boggling! The message they proclaimed was not ordinary 5 o'clock news material! It would pique everyone's interest that heard it. And not only did they proclaim it, but they challenged everyone to **dedicate their lives to it**! They expected people to believe it and even "lay their lives down" for it. And today in modernity, preachers of this same message---based on the Apostles' witness---seek disciples who will be wholly dedicated to it. These preachers (pastors, evangelists) are convinced that the **original testimony** of the Apostles was true...is true. But on what do they base this unswerving confidence? What convinces modern ministers and scholarly theologians that the Witness of the Apostles is Credible, Reliable, and Substantial for dedicating their lives to it?