And the spirit of the Egyptians within them will be emptied out, and I will confound their counsel; and they will inquire of the idols and the sorcerers, and the mediums and the necromancers...
Isaiah 19:3 ESV

Once God has decided to pass judgment on a nation, he will encourage the false prophets and teachers in their midst to that they will believe more of the lies that they already want to believe.