Joshua 8:33 a.
‘And all Israel, and their elders, and officers, and their judges, stood on this side of the Ark, and on that side, before the priests and the Levites, who bore the Ark of the covenant of YHWH, as well the stranger as the homeborn, half of them in front of Mount Gerizim and half of them in front of Mount Ebal.'
Once the sacrifices had been offered and the sacrificial meal had been partaken of, and the law recorded as a permanent reminder, the solemn covenant renewal began. The Ark of the covenant of YHWH was situated in the valley between the mountains, surrounded by the priests and the Levites who bore the Ark, And the whole nation of Israel, together with those who were strangers but welcomed among them (indicating that there were certainly some present who had not been at Sinai), stood on both sides, some in front of one mountain and some in front of the other.
‘As Moses the servant of YHWH had commanded, that they should bless the people of Israel first of all.'
All this was done in response to the commands of Moses. The old dead leader was being remembered and his instructions followed. Then would follow first the blessings. Note Moses' command that the blessing should come first.