God is not mocked. He can make people think they are being so very wise in their rejection of Him, when of course they are doing no such thing. This blinding of people's minds is part of God's sovereignty over all men.
Concerning nations which reject Him, God's providence, or sovereign power, overrules in the affairs of nations, and He can cause those nations which think that they are wiser than He is to become so immersed in their man-made philosophies, that this is in itself His judgement upon them, for those philosophies have within themselves the seeds of the nation's destruction.
Those who reject the Christian gospel are always risking being given completely over to an embracing of the foolish ideas of men, so that they become utterly blinded by the foolishness. This is an aspect of God’s judgement upon them.
How today in our nation we need to cast off the fashionable wisdom of this world, which is seeking to destroy Christianity, the Bible’s authority and indeed our whole Christian civilisation. Let us remember that “the wisdom of this world is foolishness with God” (1 Corinthians 3:19).