Why do people who expected to go to heaven end up at the Great White Throne?
They end up at the Great White Throne because they did not believe the Gospel for salvation. Although their sins were atoned for, they never appropriated God's grace and love by faith, so they stand in unbelief and must give an account of every word and deed from their rebellious life.
Les explains that these are lost people standing here because they did not believe the Gospel. Even though their sins were atoned for, they did not appropriate the grace and love of God and believe it for salvation. They stand before Him not only in unbelief but also to give an account of every word and deed they did in their life of rebellion. These are the works being judged, and there will be many awful good people standing before the Great White Throne. They had no intention of missing heaven, but they did not realize that you do not get to heaven by working your way in or by what you do; we get to heaven by simply believing that Christ's death has done it all.