It’s hard to find a theme here. It’s the gospel according to Moses, and he does bring a perspective of the mind of God to his recap of the events of his life.
The theme might be what the events of the exodus have shown us about God and how that will be useful in the promised land.
Moses describes a purposeful God who will carry out his plans despite us.
The Israelites let God down irredeemably in the desert when they made the golden calf to worship, and they should gave been destroyed there. They have no greater claim to the land though their worth than the people already there.
Those people have earned their destruction by their wickedness in their own right, is nothing to do with the holiness of the Israelites. The Israelites get their inheritance because God keeps his promises, not because they have earned it.
So don’t fear Muslims or atheists. Also don’t fear or expect that much more of Christians, who today as ever seem to do as much or more to undermine God’s kingdom.
As Bob Dylan once sang about God, he has plans of his own to set up his throne.