Luke identifies Jesus' questioners as Sadducees 'which deny that there is any resurrection.' Their elaborate case of a woman successively married to seven brothers is therefore not neutral curiosity about marriage.
It is an argument designed to make resurrection belief look incoherent.
The Sadducees were an identifiable Jewish group associated especially with priestly and aristocratic circles. Ancient sources distinguish them from Pharisees on resurrection and other matters. Their hypothetical case appeals to the Torah's levirate-marriage obligation, asking how a resurrected life could accommodate multiple legitimate marriages.
Jesus answers by distinguishing life in the present age from resurrection life and then argues from God's words to Moses—material within the Torah itself—that God is God of the living.
The historical dispute explains the structure of the exchange. Jesus is not being asked for a speculative map of heavenly marriage; he is answering an attempted reductio of resurrection.
His response rejects the assumption that resurrection simply restores present mortal social arrangements unchanged, then meets the Sadducees on scriptural ground central to their challenge.