“And you will know that I am Yahweh, for you have not walked in my statutes, nor have you carried out my judgments, but have done after the ordinances of the nations that are round about you.”
The result of what was to happen to them would bring home to them that Yahweh was not there to be trifled with. They would know that He was Yahweh. He was their covenant God, the One Who was there, the One Who controlled their destiny. But they had ignored His requirements, they had not walked in His ways and in His statutes, they had not ruled justly under His guidance and according to His will. Rather they had chosen to abide by the principles and ideas and customs taught by nations round about, worshipping their gods and walking in their ways at the same time as they claimed to belong to Yahweh. They had sunk themselves to their level, and put Yahweh on a level with the gods of other nations, powerless, amoral and ineffective.
This was in the end the reason for their certain judgment. They had forsaken the Instruction (Torah) of Yahweh, and indeed had it not been for this judgment on Israel which forced them into preserving it, and into once again recognising Yahweh for what He was, it might have been lost for ever, a huge loss to the world beyond description. God would have had to raise up another Abraham and begin again.