What will the goyim say?

All the inhabitants of the world will understand that this [destruction] is because of the sin of Israel, when they deserted the Lord their God.

(7) “Ah, my Sovereign GOD !” cried Joshua. “Why did You lead this people across the Jordan only to deliver us into the hands of the Amorites, to be destroyed by them? If only we had been content to remain on the other side of the Jordan! (8) O my Sovereign, what can I say after Israel has turned tail before its enemies? (9) When the Canaanites and all the inhabitants of the land hear of this, they will turn upon us and wipe out our very name from the earth. And what will You do about Your great name?”

Adonoy, in Your mercy, spare us, do not discard us in the hands of cruel foes. Why should the nations say: Where now is their God? For Your sake, deal kindly with us and do not delay. We beseech You, turn from Your anger, and have compassion on the treasured people whom You have chosen.

However, there is a profound wisdom in the sequence of the words the Torah quotes Moses as saying, one that contains an admonition to his people. ... by pre-empting an argument by the Jewish people that just as his prayers had been helpful when they were in the desert, similar prayers would be equally helpful once the people were in the Holy Land and they committed a major sin. The prophets in such days, they would argue, would surely be able to act as their interlocutors then just as Moses had done while he was alive.

The point Moses is making here is that at this time their atonement was only in order for G’d not to be perceived as being unable to fulfill His oath of bringing Avraham’s descendants to take over the land of Canaan. In other words, Israel’s pardon was for the sake of not desecrating G’d’s Holy name.

Once G’d had demonstrated that He had kept His promise, and that the people concerned had been settled in the Holy Land, as promised, His Holy name would never again be in danger of being desecrated by someone citing the arguments Moses had been able to cite while the people were still in the desert.

This is why Moses repeats again the wording of his prayer. He is telling the people that if his prayer had been heard, it was only on account of an irrefutable argument he had been able to advance, namely how the Egyptians and other nations would react to the Jewish people’s annihilation.

It follows, that if, G’d forbid the Jewish people, once settled in the Holy Land, would become guilty of similar misdemeanours as had the Canaanites, they would face both death and expulsion. On the contrary, if that were to happen, the gentile nations would not point to G’d’s inability to keep them there as the cause of their misfortune, but they would correctly point to the disloyalty this people had demonstrated by eschewing the laws given to them by their G’d, the One who had driven out the Canaanites. We find this all spelled out in Deuteronomy 29,23-27.