Leading up to the time of Christ, secular mythology was dominated with “heroes” who could overcome the power of death. These mythological heroes could come and go from hades at will in order to save loved ones and the like. Pop culture in the time of Jesus was ripe with this kind of thinking.
Then comes Jesus, able to raise Lazarus from the dead… then crucified and risen on the third day.
The idea of a “hero that can come and go from Hades at will” is what I believe is behind what is said about preaching to those in prison, and those who were dead in 1 Peter 3-4. This is also in accord with Jesus’ words in Revelation 1:18.
While Jesus didn’t really line up with what the Pharisees were looking for in a messiah, He did line up quite nicely with what secular culture was looking for in a savior. Pretty interesting if you ask me.
As for the rest of the quote… I can’t really speak to that except to say that the harshest words that Jesus spoke, and the sternest warnings, were to those who considered themselves “in” at the detriment of those who were “out”.