Moses knew that His Ezrach (men), Israel, would turn away from Yehovah and follow the foreign elohim (the lawmakers and judges) of all the lands that were around them.

But even now men are leaving the elohim that they have served all their lives and are returning to Yehovah. This Song of Moses is the song these men "sing" to harlot Israel in hopes that they too will return to Yehovah.