Napoleon was, by any reasonable accounting, a genius – a military mind who rewrote the rules of European warfare, a political operator who fought his way up from being a minor league Corsican nobility to the Emperor of France and ruler of most of modern Europe before he turned 35, and a reformer whose ideas around the judicial system and the liberal order still echo today.
But none of that stopped him from making one of the dumbest decisions any leader has ever made, because he was arrogant, because he’d gotten away with so much for so long that he confused his luck for a system, and because (with the exception of Talleyrand) most of the people around him had simply stopped telling him no.