In Exodus 32, what did Moses conflate when he tried to persuade God not to destroy Israel?

You mean Exodus 32, not Deuteronomy 32. After the golden calf, God is angry and wants to destroy Israel, and Moses, like a good Jewish lawyer, gives God two arguments. The first is, what will the Egyptians say, that God brought them out of Egypt with great plagues only to kill them in the mountains? That is a poor argument, because God does not act out of concern for what the Egyptians think. The second argument is where the conflation comes in. Moses says, remember your servants Abraham, Isaac, and Israel, to whom you swore that you would give their descendants all this land as an inheritance forever. But God never said He would give the physical land of Canaan to the Jews forever; if you look at all the promises from Genesis 12 to 35, you never find the word 'forever,' the Hebrew olam, attached to the land promises. What Moses does is conflate the two kinds of promises. There are the physical promises, that Abraham's physical seed would inherit the physical land of Canaan four hundred years later, which was fulfilled when Joshua took the land. And there are the spiritual promises, beginning in Genesis 12:3, that in Abraham all the families of the earth would be blessed, made when Abraham was still a Gentile and uncircumcised, as Paul stresses in Romans 4 and Galatians 3, and those are for us, the nations. By attaching 'forever' to the physical land promise, Moses gives the physical promise the stature of the spiritual one, which is exactly the conflation people make today when they claim Israel is owed the land forever.