Peter's simple word of grace had an outsized impact. Luke tells us, "When they heard these things they fell silent. And they glorified God, saying, 'Then to the Gentiles also God has granted repentance that leads to life.'”
This is God's gift - sending Jesus to save us, and sending messengers to bring his word to us. Add to that the gift of the Holy Spirit who moves our hearts to repent and believe.
I've seen short-term results from strong blasts from the pulpit. And I've seen life-changes through quiet and gentle admonition. This is the latter kind. I wish every soul was as open to this gentle message of God's grace.