As Stephen boldly continues his speech, he comes to the time of Moses and the Exodus. This is not by mistake. God said that he would set the people free, and this initiative was of God's doing. Moses was an important part, but it was still God's work. Not to spoil the next point in Stephen's sermon, but what Jesus did was the same: God came to do the work of redemption, and it was God's own work to do.