Paul gave his testimony to the king. I suspect if he was a free preacher, not a prisoner, he wouldn't have had the opportunity. As Paul spoke he wove a story that combined narrative about what happened and the claims of Jesus!
The line in his vision, "It is hard to kick against the goads!" is recorded only here. That is to say, it is a hard life to actively oppose Christ.
The way Paul concludes his testimony is interesting. He was sent to open the eyes of the Gentiles, to turn them from darkness to light, from the authority of Satan to the authority of God and to offer forgiveness of sin. What a calling! What a job description!
Paul pressed Agrippa to believe. Even kings need to believe.
I wonder about God's sovereignty again. Paul could have gone free except he appealed to Caesar. Why? Why not let him go anyway, God?