There is a doctrine called the depravity of man. It basically takes the position that due to the Fall, mankind has no desire for God, mankind enjoys being at enmity with God, and mankind (apart from the grace of God) will not seek Him.
There is nothing that demonstrates this principle more than the end of Christ's Millennial Reign. When Jesus returns after the Great Tribulation, He will come with the saints. Jesus will be in the presence of everyone for 1,000 years. So will all of the saints of the Bible. In today's world, men can doubt the validity of the Bible and can claim that much of it is anecdotal or fabrication, but it will not be that way during the Millennial Reign. You don't believe the story of the Flood? Ask Noah. He will be there. You don't believe the story of Job? Ask him. He will be there. You don't believe Daniel wrote all of the prophecies recorded in his book? Ask him. You think the Gospel writers or early church leaders manipulated the Gospels? Ask them.
Yet, in spite of all the evidence that will be available, in spite of the presence of Christ Himself, when the 1,000 years comes to an end, Satan will gather a huge army to fight against the Lord. How can that be? It's the condition of man.
Think about it: the Jewish Holocaust was less than 100 years ago. People who lived through it are still alive today. There are museums with artifacts still around. The death camps are still there. Yet, people deny that the Holocaust ever occurred. Even though astronauts who walked on the moon are still alive today, people don't believe they went there. Even though they left mirrors there that can bounce lasers back to earth, people still don't believe it.
It will be the same during the Millennial Reign with the exceptions that because natural man is depraved and because Satan is working to deceive them, it will be worse.