The debate between Jesus and Sadducees about the resurrection and the seven brothers who married the same woman and all died took place right after His debate on paying taxes to the Emperor. In the earlier debate, Jesus said, "Give to Caesar what belongs to Caesar and to God what belongs to God." In both debates, we see that Jesus' opponents are those who have the perception that the Kingdom of God is a political structure that will exist on earth under a Jewish King. So, their understanding of the Kingdom of God depends only on earthly prosperity and security. Their expectation of the Messiah is the ruler who will bring back the glorious past and God's rule through safe borders and prosperity. But Jesus is pointing toward the resurrection and eternal life, where the raised people will be like angels and never die again. Furthermore, Luke alludes to the story of Moses, who revealed that the dead are raised in the story of the burning bush. The story of the burning bush was intended to prove that Moses does indeed teach about the resurrection.
The faith in eternal life and the eschatological kingdom of God is not easy to sell. We are currently living in a world that is bombarded by the utopian of establishing heaven on the heart. On the one hand, there is a Marxist utopia in its variation and forms, which believes that revolution and distribution of assets and income will create heaven on earth. Everything will be all right once everybody gets their own shares and benefits. On the other hand, there is a liberal form of utopia, which believes that everything will be all right with economic growth and technological progress. They may come with some variants, including the distribution of income and welfare, but the ultimate goal is to establish peace, justice, and abundance on Earth. But all those utopias forgot that humans will always remain human with flaws and freedoms. It is only Jesus who changes our human hearts and points us to the ultimate end, which is eternal life.