As Stephen did with Joseph, he likewise did with Moses - he preached Christ (without mentioning His name) by his selective summation of Moses' life (his initial rejection and eventual acceptance as Israel's deliverer).  He wanted them to see that Jesus was very much the Fulfillment of Moses' words about the Messiah being "a Prophet . . . like unto me" (Deut. 18:15).

In this lesson, Stephen got into the second phase of Moses' life (his second 40-year life segment), when he made his first "visit" to his people as their deliverer and was rejected and then vanished from sight (presumed dead) as he lived with the Gentiles (Midianites).

Stephen's underlying message to the Jews of his day was that unless they wanted to continue to follow the pattern of their forefathers, who betrayed and rejected the ones (Joseph and Moses) who God providentially "raised from the dead" to be their deliverers, they should repent for having done exactly the same with Jesus!