Another possibility is that God is making Biden look like a fool by making him truly insane.

The same way God made Nebuchadnezzar insane for 7 years until he acknowledged God’s complete power over any mortal man, even a king.

Daniel 4:28-37 28 All this happened to King Nebuchadnezzar. 29 Twelve months later, as the king was walking on the roof of the royal palace of Babylon, 30 he said, “Is not this the great Babylon I have built as the royal residence, by my mighty power and for the glory of my majesty?” 31 Even as the words were on his lips, a voice came from heaven, “This is what is decreed for you, King Nebuchadnezzar: Your royal authority has been taken from you. 32 You will be driven away from people and will live with the wild animals; you will eat grass like the ox. Seven times will pass by for you until you acknowledge that the Most High is sovereign over all kingdoms on earth and gives them to anyone he wishes.” 33 Immediately what had been said about Nebuchadnezzar was fulfilled. He was driven away from people and ate grass like the ox. His body was drenched with the dew of heaven until his hair grew like the feathers of an eagle and his nails like the claws of a bird. 34 At the end of that time, I, Nebuchadnezzar, raised my eyes toward heaven, and my sanity was restored. Then I praised the Most High; I honored and glorified him who lives forever. His dominion is an eternal dominion; his kingdom endures from generation to generation. 35 All the peoples of the earth are regarded as nothing. He does as he pleases with the powers of heaven and the peoples of the earth. No one can hold back his hand or say to him: “What have you done?” 36 At the same time that my sanity was restored, my honor and splendor were returned to me for the glory of my kingdom. My advisers and nobles sought me out, and I was restored to my throne and became even greater than before. 37 Now I, Nebuchadnezzar, praise and exalt and glorify the King of heaven, because everything he does is right and all his ways are just. And those who walk in pride he is able to humble.