Isaiah 48 -Elohim didn’t want Israel to think their punishment came from false gods, it was from Him

Isa 48:4
"Because I know that you are obstinate, And your neck is an iron sinew, And your forehead bronze,
Elohim knew they were a stiff-neck, hard-headed people (Ezekiel 3:4-11).
Isa 48:5
Therefore I declared them to you long ago, Before they took place I proclaimed them to you, Lest you should say, 'My idol has done them, And my graven image and my molten image have commanded them.'
Elohim did not want Israel to think that their punishment came from false gods. He said it long ago so they would know it came from Him. Sure enough, they ended up attributing their woes to their false gods.
Jer 44:15-18 Then all the men who were aware that their wives were burning sacrifices to other gods, along with all the women who were standing by, as a large assembly, including all the people who were living in Pathros in the land of Egypt, responded to Jeremiah, saying, 16“As for the message that you have spoken to us in the name of the LORD, we are not going to listen to you! 17“But rather we will certainly carry out every word that has proceeded from our mouths, by burning sacrifices to the queen of heaven and pouring out libations to her, just as we ourselves, our forefathers, our kings and our princes did in the cities of Judah and in the streets of Jerusalem; for then we had plenty of food, and were well off, and saw no misfortune. 18“But since we stopped burning sacrifices to the queen of heaven and pouring out libations to her, we have lacked everything and have met our end by the sword and by famine.”
Isa 48:3 "I declared the former things long ago And they went forth from My mouth, and I proclaimed them. Suddenly I acted, and they came to pass.
Elohim declared long ago the things that would happen to them.
Josh 23:15-16 “And it shall come about that just as all the good words which the LORD your God spoke to you have come upon you, so the LORD will bring upon you all the threats, until He has destroyed you from off this good land which the LORD your God has given you. 16“When you transgress the covenant of the LORD your God, which He commanded you, and go and serve other gods, and bow down to them, then the anger of the LORD will burn against you, and you shall perish quickly from off the good land which He has given you.”
Leviticus 26 and Deuteronomy 28 give vivid details as to what their future held when they ignored His Torah. Those things would come to pass.