Spoiler alert for the rest of the Old testament.
Moses continues his final words before they all go to the promised land without him.
He focuses on the ban against idols. He wants them not to forget about it after a few generations or they will be overrun and exiled. He says that even if that happens God’s mercy will mean they are eventually returned. As I said, spoiler alert.
The overall message is that there is one true God who deserves obedience. It serves as an introduction to a dissertation of the law.
One true God. If he is forgotten and other gods take over, it is a disaster, but his abiding character is mercy, and he will bring us back.