Belshazzar would have certainly heard about his grandfather going mad and afterwords finally turning to God. Yet, Belshazzar did the thing that was so wicked it caused the kingdom to fall.
Each arrogant person, including world leaders, celebrities and business tycoons, will one day commit the act in their lives that will push God over the edge, so to speak. When that act has happened, God will say "That's it" and, just like Belshazzar, their lives will be over.
Better to learn from Nebuchadnezzar, you world leaders, famous people and rich businessmen, along with everybody else.
Humble yourselves before God humbles you. It's a far more pleasant experience to humble yourself before God than to be humbled by God.